Microneedles and methods of manufacture thereof

ABSTRACT

A microneedle array is provided for administrating a drug or other substance into a biological tissue. The array includes a base substrate; a primary funnel portion extending from one side of the base substrate; and two or more solid microneedles extending from the primary funnel portion, wherein the two or more microneedles comprise the substance of interest. Methods for making an array of microneedles are also provided. The method may include providing a non-porous and gas-permeable mold having a two or more cavities each of which defines a microneedle; filling the cavities with a fluid material which includes a substance of interest and a liquid vehicle; drying the fluid material to remove at least a portion of the liquid vehicle and form a plurality of microneedles that include the substance of interest, wherein the filling is conducted with a pressure differential applied between opposed surfaces of the mold.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/983,593, filed Apr. 24, 2014, which is incorporated herein byreference.

BACKGROUND

The present application is generally in the field of microneedle for thetransport of therapeutic, diagnostic, cosmetic, biological or othermolecules into, out of or across the skin or other tissue barriers.

Microneedles are small in size, which allows them to precisely targetsuperficial tissue layers (e.g., skin) and to be relatively pain free indoing so. However, their small size may hinder other factors that areimportant for their functionality and/or manufacture. This isparticularly true in the case of producing a microneedle patch fortransdermal drug delivery.

For example, since microneedles are short in length in comparison to thebase or backing from which they are formed or affixed to, tissueinsertion can be difficult. This results from the elastic nature of thetargeted tissue (e.g., skin) because much of the applied force whenadministering them to skin is used to deform the skin underneath theentirety of the microneedle patch in order for the microneedles tosufficiently contact and penetrate the tissue. Therefore, the patchapplication force required for successful microneedle insertion can behigher than the force to insert the microneedles alone. This hasresulted in the development of complex and aggressive applicators thatapply microneedle patches to the skin with impact. This adds cost andcomplexity, which are undesirable.

Conventional molding methods generally are not well suited for makingmicroneedle arrays in a simple, fast, highly reproducible and accuratemanner. For example, the small size of the microneedles limits theamount of material that can be loaded into them during manufacturing (inthe case of delivery) or that can be sampled/extracted in the case ofanalyte sampling/monitoring. The microneedles have a limited volume,which is similar to the mold cavities from which they are manufactured.This limits the amount of material that can be loaded into them. Makingthis more challenging is the fact that many molecules of interest havelimited solubility in water (one of the preferred carrier solventsduring manufacturing) and other solvents.

Manufacturing of small solid microneedles also may suffer frominaccuracies arising from use of conventional fluid dispensing systemsand conventional molds. The inaccuracies may stem from misalignmentbetween deposited drops to microneedle cavities and highly variable fillvolumes. The small size of the microneedle mold cavities makes themdifficult to target with direct deposition technologies especiallyduring high-volume manufacturing. The targeted deposition area isdefined by the opening of a microneedle cavity in the mold, which isvery small. The volume of a microneedle also is very small, generally onthe order of 10 nanoliters, which is difficult to reproducibly depositusing microliter and nanoliter dispensing systems in a high volumemanufacturing environment. There remains a need for fast, reproducible,accurate filling of microneedle molds.

In sum, there remain needs to improve microneedle designs for bettertissue insertion and to improve microneedle production methods,particularly for such improved designs.

SUMMARY

Improved microneedle arrays and drug delivery patches, along withimproved methods of making microneedle arrays, have been developed whichaddress one or more of the foregoing needs.

In one aspect, a microneedle array is provided for administration of asubstance of interest into a biological tissue. In an embodiment, thearray includes a base substrate having a microneedle side and anopposing back side; at least one primary funnel portion extending fromthe microneedle side of the base substrate; and two or more solidmicroneedles extending from the at least one primary funnel portion,wherein the two or more solid microneedles comprise a substance ofinterest. In one embodiment, each of the two or more solid microneedlesfurther comprises a secondary funnel portion extending from the at leastone primary funnel.

In another aspect, a microneedle patch is provided for administration ofa substance of interest into a biological tissue. In an embodiment, thedevice includes a base substrate having a microneedle side and anopposing back side; a primary funnel portion extending from themicroneedle side of the base substrate; and one or more solidmicroneedles extending from the primary funnel portion, wherein the oneor more solid microneedles comprise a substance of interest and one ormore matrix materials, and wherein more of the substance of interest islocated in the one or more solid microneedles than is located in theprimary funnel portion.

In still another aspect, a microneedle patch is provided foradministration of two or more substances of interest into a biologicaltissue. In one case, the patch includes a base substrate having amicroneedle side and an opposing back side; a first funnel portionextending from the microneedle side of the base substrate, wherein thefirst funnel portion is elongated in a direction parallel to the basesubstrate; and a first array of two or more solid microneedles extendingfrom the first funnel portion, wherein the microneedles of the firstarray comprise a first substance of interest; a second funnel portionextending from the microneedle side of the base substrate, wherein thesecond funnel portion is elongated in a direction parallel to the basesubstrate; and a second array of two or more solid microneedlesextending from the second funnel portion, wherein the microneedles ofthe second array comprise a second substance of interest, which isdifferent from the first substance of interest.

In yet another aspect, methods are provided for making an array ofmicroneedles. In one embodiment, the method includes (a) providing amold having an upper surface, an opposed lower surface, and an openingin the upper surface, wherein the opening leads to a first cavityproximal to the upper surface and to a second cavity below the firstcavity, wherein the first cavity defines a primary funnel portion, andwherein the second cavity defines at least one microneedle; (b) fillingat least the second cavity, via the opening in the mold, with a firstmaterial which comprises a substance of interest dissolved or suspendedin a first liquid vehicle; (c) drying the first material in the mold toremove at least a portion of the first liquid vehicle to form at least atip portion of a microneedle in the second cavity, wherein the tipportion comprises the substance of interest; (d) filling the firstcavity, and the second cavity if any is unoccupied following steps (b)and (c), via the opening in the mold, with a second material whichcomprises a matrix material dissolved or suspended in a second liquidvehicle; (e) drying the second material in the mold to remove at least aportion of the second liquid vehicle to form (i) a primary funnelportion, and (ii) any portion of the at least one microneedle unformedfollowing steps (b) and (c), wherein the primary funnel portioncomprises the matrix material; and (f) removing from the mold the atleast one microneedle together with the primary funnel portion connectedthereto, wherein more of the substance of interest is located in the atleast one microneedle than is located in the primary funnel portion.

In another aspect, a method is provided for making an array ofmicroneedles, which includes (a) providing a non-porous andgas-permeable mold having an upper surface, an opposed lower surface,and a plurality of openings in the upper surface, wherein each openingleads to a cavity which defines a microneedle; (b) filling the cavities,via the openings, with a fluid material which comprises a substance ofinterest dissolved or suspended in a liquid vehicle; (c) drying thefluid material in the mold to remove at least a portion of the liquidvehicle and form a plurality of microneedles which comprise thesubstance of interest; and (d) removing the plurality of microneedlesfrom the mold, wherein the filling of step (b) is conducted with apressure differential applied between the upper and lower surfaces ofthe mold.

In a further aspect, a method is provided for making an array ofmicroneedles, which includes providing a two-part mold having a upperportion and a lower portion, the upper portion having an upper surface,an opposed lower surface, and an opening extending therethrough, theopening defining an upper cavity, the lower portion having an uppersurface, an opposed lower surface, and an opening in the upper surfacewhich is in fluid communication with the upper cavity and which leads toa lower cavity, the lower cavity defining a microneedle, wherein theupper portion and the lower portion are separably secured together;filling at least the lower cavity, via the opening in the upper portion,with a first material which comprises a substance of interest dissolvedor suspended in a first liquid vehicle; drying the first material in themold to remove at least a portion of the first liquid vehicle to form amicroneedle which comprises the substance of interest; and removing themicroneedle from the mold.

Additional aspects will be set forth in part in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the aspects described below. The advantagesdescribed below will be realized and attained by means of the elementsand combinations particularly pointed out in the appended claims. It isto be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-12 illustrate various embodiments of microneedle arrays,microneedle patches, and microneedle structures which include a funnelportion.

FIGS. 13-16, 18-21, and 25-27 illustrate various methods, molds, andsystems for making microneedle arrays, as described herein.

FIGS. 17 and 22-24 show some example embodiments of microneedle arraysand properties thereof as produced using some of the methods and systemsdescribed herein.

DETAILED DESCRIPTION

Improved microneedle arrays and methods of manufacture have beendeveloped. In embodiments, the microneedles include an activepharmaceutical ingredient or other substance of interest, and arrays ofthese microneedles are particularly suited for use as/in drug deliverypatches, such as for application to a patient's skin.

In embodiments, the microneedle arrays advantageously include one ormore funnel portions between the base substrate and the microneedlesthemselves. The addition of a funnel portion (sometimes referred toherein as a “funnel,” a “funnel portion,” a “primary funnel portion,” a“secondary funnel portion,” or a “funnel lead-in”) imparts certainadvantages in its use, its manufacture, or in both its use andmanufacturing.

First, tissue insertion difficulties may be lessened by incorporatingfunnels into the microneedle patch, because they raise the microneedlesoff their base or backing layer allowing the microneedles to more simplycontact and penetrate the targeted tissue—without having to make themicroneedles longer. This increases the microneedle insertion efficiency(e.g., success rate of microneedle penetration) and decreases the amountof force required to successfully apply a microneedle patch. That is, alarger number of the collection of microneedles puncture the tissue (forexample, greater than or equal to 80% or 90% or 95% of the microneedlesin a patch) or a larger fraction of each microneedle penetrates into theskin (for example, an average of greater than or equal to 50% or 75% or80% or 90% of 95% of the length or the volume of the microneedles in apatch). The net result of either of these measures of microneedlepenetration success rate is that a larger portion of a substance ofinterest being administered by the microneedles is delivered into thetissue.

This approach to microneedle design can also be forgiving, allowingmicroneedle insertion with little to no funnel insertion after applyinga minimum force. That is, the resulting insertion depth of themicroneedles with funnels is less sensitive to the application ofexcessive force during patch application because the rapid expansion ofthe funnel section hinders insertion and results in insertion up to themicroneedle-funnel interface. This allows them to be inserted by simplethumb pressure alone, thumb pressure with a mechanism to indicate theminimum required force has been applied, or simpler and less aggressiveapplicators that may not rely on impact. For example, if an array oflonger microneedles is pressed against the skin, it is possible to onlypartially insert the microneedles, allowing them to still penetrateshallowly. However, the actual depth of microneedle insertion is verydifficult to control since the minimum force required will vary due todifferences between individuals (e.g., skin types) and application sites(e.g., locations on a patient's body). Therefore, the insertion force topartially insert an array of longer microneedles will vary and byapplying a force that is too small or too large will result in impropermicroneedle insertion depth. This is alleviated when using microneedleswith funnel lead-ins because the rapid expansion of the funnel portionlimits insertion depth. If the minimum force (or greater) has beenapplied, the insertion depth is consistent.

Second, loading and filling limits may be significantly lessened byincluding funnels in a microneedle device, because they increase theamount of a substance of interest that can be loaded into themicroneedles during their manufacture. In a molding process thatincludes funnels, the amount of the substance that can be loaded isgreater than the volume of the microneedle cavities multiplied by theconcentration of the substance in the solution being loaded. The amountloaded can be as large as the microneedle and funnel volumes combinedmultiplied by the concentration of the filling solution/suspensionmultiplied by the number of filling steps. The funnel volume is oftenmany times greater than the microneedle volume thereby significantlyincreasing the amount that can be loaded into the microneedles.

Third, manufacturing challenges can be significantly lessened by addingfunnels, because they greatly increase the target area during a moldfilling step, since the funnels expand out from the microneedle cavity.This larger area target (i.e., funnel-base interface) greatly relaxesthe positional accuracy required for the deposition/filling systemcompared to a mold containing no funnels, in which the target area wouldbe the microneedle-base interface. In addition, the volume to fill amicroneedle with a funnel can be many times greater than the microneedleitself, thereby reducing this constraint too.

Other advantages and benefits of the microneedle array designs and themethods of manufacture that have been developed are described throughoutthe rest of the specification. Certain of the improved manufacturingmethods are applicable to microneedle arrays that include funnelportions, as well as to microneedle arrays that do not include funnelportions.

Unless otherwise defined herein or below in the remainder of thespecification, all technical and scientific terms used herein havemeanings commonly understood by those of ordinary skill in the art towhich the present disclosure belongs. It is also to be understood thatthe terminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting. In describing andclaiming the present embodiments, the following terminology will be usedin accordance with the definitions set out below.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. Thus, for example, reference to “acomponent” can include a combination of two or more components;reference to “a buffer” can include mixtures of buffers, and the like.

The term “about”, as used herein, indicates the value of a givenquantity can include quantities ranging within 10% of the stated value,or optionally within 5% of the value, or in some embodiments within 1%of the value.

1. MICRONEEDLE ARRAYS WITH FUNNEL PORTION

The microneedle arrays include a base substrate and two or moremicroneedles which extend from a surface of the base substrate. Eachmicroneedle has a proximal end attached to the base substrate directly,or indirectly via one or more funnel portions, and a distal tip endwhich is sharp and effective to penetrate biological tissue. Themicroneedle has tapered sidewalls between the proximal and distal ends.

The funnel portion may be integrally formed with the microneedle. Theouter surface of the funnel portion can be distinguished from themicroneedle portion of the protruding structure by the distinctchange/expansion in the angle of the surfaces defining the differentportions of the structure, which can be seen as a rapid expansion in atleast one dimension (e.g., radially) as one progresses from the distalend toward the proximal end of the microneedle. The funnel portion iswider at its base end than its microneedle end. This expansion may bedesigned so that little to no funnel portion is inserted into thetargeted tissue layer or space.

In a preferred embodiment, a microneedle array is provided foradministration of a drug or other substance of interest into abiological tissue such as skin, wherein the array includes a basesubstrate having a microneedle side and an opposing back side; a primaryfunnel portion extending from the microneedle side of the basesubstrate; and one or more solid microneedles extending from the primaryfunnel portion, wherein the one or more solid microneedles comprise asubstance of interest and a matrix material, and wherein more of thesubstance of interest is located in the one or more solid microneedlesthan is located in the primary funnel portion. For example, the primaryfunnel portion may include from 0% to 20% of the substance of interestpresent in the combination of the one or more solid microneedles and theprimary funnel portion from which the one or more solid microneedlesextend. This embodiment advantageously avoids wasting the drug in thefunnel portion.

In an embodiment, a microneedle array is provided for administration ofa drug or other substance of interest into a biological tissue such asskin, wherein the array includes a base substrate having a microneedleside and an opposing back side; at least one primary funnel portionextending from the microneedle side of the base substrate; and two ormore solid microneedles extending from the at least one primary funnelportion, wherein the two or more solid microneedles comprise a substanceof interest. Each of the two or more solid microneedles may furtherinclude a secondary funnel portion extending from the at least oneprimary funnel.

FIGS. 1-2 show one example of a microneedle array 105 as part of amicroneedle patch 100, wherein each microneedle 130 extends from afunnel portion 125. The microneedle array 105 includes a base substrate110 having a microneedle side 115 and an opposing back side 120. Thefunnel portions 125 extend from the microneedle side 115 of the basesubstrate 110. The microneedle array 105 is affixed to a handling layer140 by an adhesive layer 135 disposed there between. The handling layer140 includes a tab portion 145 that extends away from the microneedlearray. The tab portion 145 enables a person to manually hold andmanipulate the microneedle patch 100 without having to contact themicroneedles 130. An adhesive cover 150 is affixed to a portion of theadhesive layer 135 that overlays the tab portion 145 of the handlinglayer 140. The adhesive cover 150 enables a person to manually hold andmanipulate the microneedle patch 100 without having to contact theadhesive layer 135.

An optional mechanical force indicator 155 is disposed between theadhesive layer 135 and the handling layer 140. The mechanical forceindicator may be used to indicate to a person the amount of force and/orpressure applied to the patch during its use. For example, in oneembodiment, the indicator is configured to provide a signal when a forceapplied to the patch by a person (in the course of applying the patch toa patient's skin to insert the one or more microneedles into thepatient's skin) meets or exceeds a predetermined threshold. Thepredetermined threshold is the minimum force or some amount greater thanthe minimum force that is required for a particular microneedle patch tobe effectively applied to a patient's skin. That is, it is the forceneeded to cause the microneedles to be properly, e.g., fully, insertedinto a patient's skin.

Structural Features of the Funnel Portion and the Microneedle

The funnel portion can be formed into a variety of differentconfigurations. The funnel portion can have tapered walls (steeply orshallowly), ‘stepped’ walls, tapered walls that then become vertical,hemispherical walls, or a combination thereof. Funnel portions can besymmetric or asymmetric. Some of these configurations are illustrated inthe cross-sectional views shown in FIGS. 3A-3F. FIG. 3A shows a coneshaped funnel portion 310 which has a straight tapered sidewall andmicroneedle 300 extending therefrom. FIG. 3B shows a funnel portion 320with a stepped sidewall and a microneedle 300 extending therefrom. FIG.3C shows a funnel portion 330 with a sidewall that has both a taperedportion and an untapered (vertical) portion and a microneedle 300extending therefrom. FIG. 3D shows an axially asymmetric funnel portion340 with a sidewall that tapers at a different angle on one side 341 ofthe funnel portion as compared to another (e.g., opposed) side 342 ofthe funnel portion, with a microneedle 301 extending therefrom. FIG. 3Eshows a shallow cone shaped funnel portion 350 which has a straighttapered sidewall and a microneedle 300 extending therefrom. FIG. 3Fshows a hemispherical shaped funnel portion 360 which has a curvedsidewall and a microneedle 300 extending therefrom.

A single microneedle array or patch may have funnel portions having twoor more different geometries. For example, an array could include onerow of microneedles having funnel portions of a first size or shape anda second row of microneedles having funnel portions of a second size orshape. For example, the differences could be beneficially designed fordelivering two different substances of interest.

Manufacturing and use considerations also drive the selection of thegeometry of the funnel portion. For example, the density of themicroneedles and funnels within an array (i.e., the spacing) may also bebalanced with microneedle/funnel geometry to allow for simple needleinsertion with little to no funnel insertion (i.e., because more closelyspace microneedles are generally more difficult to insert). As anotherexample, during manufacturing, a volume of solution is deposited intothe funnel portions of a mold and when dried/cured, the solutesubstantially migrates into the microneedle and its tip portion of themold. The funnel shape, in one embodiment, is designed to promote andmaximize this solute migration.

The length of a microneedle (L_(MN)) may be between about 50 μm and 2mm. In most cases they are between about 200 μm and 1200 μm, and ideallybetween about 500 μm and 1000 μm. The length (height) of a funnel(L_(FUN)) may be between about 10 μm and 1 cm. In most cases funnels arebetween about 200 μm and 2000 μm, and more preferably between about 500μm and 1500 μm. The ratio L_(FUN)/L_(MN) may be between about 0.1 and10, more typically between about 0.3 and 4 and more preferably betweenabout 0.5 and 2 or between about 0.5 and 1, although a ratio betweenabout 1 and 2 is also useful. The ratio L_(FUN)/L_(MN) could be lessthan about 1 or could be greater than about 1. The sum L_(MN)+L_(FUN)may be between about 60 um and 1.2 cm, more typically between about 300um and 1.5 mm and more preferably between about 700 um and 1.2 mm.L_(MN)+L_(FUN) can be greater than about 1 mm, or greater than about 1.2mm or greater than about 1.5 mm.

The volume of a microneedle (V_(MN)) can be between about 1 nl and 100nl. In most cases, it is between about 5 nl and 20 nl. The volume of afunnel (V_(FUN)) can be about 1 nl to 20,000 nl, more typically betweenabout 5 nl and 1000 nl and more preferably between about 10 nl and 200nl. The ratio V_(FUN)N_(MN) can be between about 0.1 to 100, moretypically between about 0.5 and 20 and more preferably between about 1and 10 or between about 2 and 5.

The cross-sectional area of the microneedle where it meets the funnel(A_(MN-FUN)) is between about 300 μm² and 800,000 μm². In most cases itis between about 10,000 μm² and 500,000 μm² and more preferably betweenabout 50,000 μm² and 200,000 μm². The cross-sectional area of thefunnel-base interface (A_(FUN-BASE)) is between about 301 μm² and 8×10⁷μm², more typically between about 10,000 μm² and 5×10⁶ μm² and morepreferably between about 100,000 μm² and 2×10⁶ μm². The ratioA_(FUN-BASE)/A_(MN-FUN) is always greater than 1, because the funnelexpands out from the microneedle. The ratio A_(FUN-BASE)/A_(MN-FUN) isbetween about 1.1 to 2500, more typically between about 1.5 and 100 andmore preferably between about 2 and 10.

The one or more microneedles may be arranged on a base substrate in anysuitable density. For example, a plurality of microneedles may bearranged in even or staggered rows in an array, wherein each microneedleis separated from its nearest neighboring microneedle by a distanceabout equal to the height of the microneedle.

The width at the microneedle-funnel interface (W_(MN-FUN)) is betweenabout 20 μm and 1000 μm. In most cases it is between about 100 μm and500 μm and more preferably between about 200 μm and 400 μm. The width atthe funnel-base interface (W_(FUN-BASE)) is between about 30 μm and 1cm, more typically between about 300 μm and 1500 μm and more preferablybetween about 500 μm and 1000 μm. The ratio W_(FUN-BASE)/W_(MN-FUN) isalways greater than 1, because the funnel expands out from themicroneedle. The ratio W_(FUN-BASE)/W_(MN-FUN) can be between about 1.1and 50, more typically between about 1.5 and 10 and more preferablybetween about 2 and 5.

The funnel portion expands from the location where it connects to themicroneedle in at least one dimension. In most cases it expandsradially. The minor angle α is located between a line that extends fromthe funnel-microneedle interface to where the funnel portion meets thebase and a line that extends from the same point and is perpendicularthe central axis of the microneedle, as shown in FIGS. 4A-4C. The angleα is less than about 90°, but greater than about 10°. In most cases itis between about 30° and 75° and more preferably between about 45° andabout 60°.

Each microneedle can be associated with one funnel and each funnelassociated with one microneedle. Alternatively, one microneedle can beassociated with more than one funnel. Alternatively, one funnel can beassociated with more than one microneedle. In general, on a per patchbasis the number of microneedles ≥number of funnels. However, the numberof funnels may exceed the number of microneedles when the funnels areused in series. The number of microneedles per patch is generallybetween 1 and 10,000, and in most cases is between about 20 and 1000 andmore preferably between about 50 and 500. The number of funnels perpatch is generally between about 1 and 10,000, and in most cases isbetween about 5 and 500 and more preferably between about 10 and 500.The ratio of funnels to microneedle is between about 0.01 to 10, moretypically between about 0.05 and 4 and more preferably between 0.1and 1. In some cases, the ratio of funnels to microneedle is about 1. Inother cases, the ratio of funnels to microneedle is about 2 or greater.In some cases, a plurality of microneedles all in a row is associatedwith the same funnel. In some cases, some of the microneedles areassociated with funnels and other microneedles are not associated withfunnels. In some cases, the number of funnels that each microneedle isassociated with within a patch is not the same for all microneedles orfor all funnels.

Funnels can also be used in series, i.e., a collection of funnels wherethe first funnel (i.e., a primary funnel portion) (base end) feeds anumber of other funnels (i.e., secondary funnel portions). For example,each microneedle may have its own funnel and a row or section of a patchof microneedles and funnels may be connected to a larger elongatedfunnel. This is particularly useful when filling a microneedle patchwith multiple actives for one reason or another (e.g., actives areincompatible with one another, formulated differently for stabilityand/or release kinetics). For example, some microneedles could releasethe active rapidly thereby providing an immediate burst to raise theblood levels of the active into the therapeutic range quickly and othermicroneedles could be designed to release the active slowly to keep theblood levels of the active in the therapeutic range for an extendedperiod of time. Alternatively, a single large funnel may be connected toan entire microneedle (with or without their own separate funnels)patch. This may be useful for filling of a single active.

FIGS. 5-8 illustrate various embodiments of microneedle arrays thatcomprise multiple microneedles with one funnel portion.

In one embodiment, as illustrated in FIGS. 5 and 6, a microneedle array505 that includes a base substrate 510 with a microneedle side 515 andan opposing back side 520. The microneedle array 505 also includes threesets of microneedles 530 with each set having one funnel portion 525extending from the microneedle side 515 of the base substrate 510. Asshown, the microneedle tip portion includes a substance of interest, butthe funnel portion 525 and base substrate portion 510 contains little tono substance of interest. Each funnel portion 525 is elongated in adirection (D) that is parallel to the base substrate 510. In thisembodiment, the microneedles 530 of all three elongated funnel portions525 contain the same substance of interest.

In other embodiments, different sections of the microneedle array maycontain different substances of interest and/or excipients, for example,as illustrated in FIGS. 7 and 8. The microneedle array 705 includes abase substrate 710 with a microneedle side 715 and an opposing back side720. The microneedle array 705 also includes three sets of microneedles730 a, containing a first substance of interest, and three sets of othermicroneedles 730 b, containing a second substance of interest, with eachset having one funnel portion 725 extending from the microneedle side715 of the base substrate 710. Each funnel portion 725 is elongated in adirection (D) that is parallel to the base substrate 710.

FIGS. 9-12 illustrate various embodiments of microneedle arrays thatcomprise multiple microneedles with two funnel portions, a primaryfunnel portion and a secondary funnel portion.

In one embodiment, as illustrated in FIGS. 9 and 10, a microneedle array905 that includes a base substrate 910 with a microneedle side 915 andan opposing back side 920. The microneedle array 905 also includes threesets of microneedles 930 with each set having a primary funnel portion925 extending from the microneedle side 915 of the base substrate 910and secondary funnel portions 935 extending from the primary funnelportion 925. Each primary funnel portion 925 is elongated in a direction(D) that is parallel to the base substrate 910. In this embodiment, themicroneedles 930 and funnel portions 925, 935 contain the samesubstances of interest and excipients, respectively.

In other embodiments, different sections of the microneedle arraycontain different substances of interest and/or excipients, for example,as illustrated in FIGS. 11 and 12. The microneedle array 1105 includes abase substrate 1110 with a microneedle side 1115 and an opposing backside 1120. The microneedle array 1105 also includes three sets ofmicroneedles 1130 a, containing a first substance of interest, and threesets of other microneedles 1130 b, containing a second substance ofinterest, with each set having a primary funnel portion 925 extendingfrom the microneedle side 1115 of the base substrate 1110 and secondaryfunnel portions 1135 extending from the primary funnel portion 1125.Each funnel portion 1125, 1135 is elongated in a direction (D) that isparallel to the base substrate 1110.

A microneedle patch such as the foregoing could also be manufactured byautomated pick-n-place type manufacturing, where each separate region ofthe patch containing a different formulation is molded separately andthen assembled onto an adhesive pad or backing.

A microneedle patch may include different microneedles, for examplecontaining different compositions of materials, including differentactives and/or excipients and/or other materials. Microneedles thatcontain the same composition of materials may be connected to commonfunnel(s). In addition to different microneedles, rows, or regionshaving different material loaded within them, the microneedles andfunnels themselves may have discrete layers of materials. The discretelayers may appear to be in a stacked, or striped, form as shown in FIG.15, or the discrete layers may be in the form of shell layers startingfrom the sidewall of the cavity in the mold inward, as shown in FIG. 16.

Substance of Interest/Active Pharmaceutical Ingredient

A wide range of substances may be formulated for delivery to biologicaltissues with the present microneedles and methods. As used herein, theterm “substance of interest” includes active pharmaceutical ingredients,allergens, vitamins, cosmetic agents, cosmeceuticals, diagnostic agents,markers (e.g., colored dyes or radiological dyes or markers), and othermaterials that are desirable to introduce into a biological tissue. The“substance of interest” is sometimes referred to herein as “the active.”In a preferred embodiment, the biological tissue is a tissue of a humanor other mammal, including but not limited to the skin of human or othermammal. In an alternative embodiment, the biological tissue is a planttissue.

In one embodiment, the substance of interest is a prophylactic,therapeutic, or diagnostic agent useful in medical or veterinaryapplication. In one embodiment, the substance of interest is aprophylactic or therapeutic substance, which may be referred to hereinas an API. In certain embodiments, the API is selected from suitableproteins, peptides and fragments thereof, which can be naturallyoccurring, synthesized or recombinantly produced. Representativeexamples of types of API for delivery include antibiotics, antiviralagents, analgesics, anesthetics, antihistamines, anti-inflammatoryagents, anti-coagulants, allergens, vitamins, antineoplastic agents.

In one embodiment, the substance of interest comprises a vaccine.Examples of vaccines include vaccines for infectious diseases,therapeutic vaccines for cancers, neurological disorders, allergies, andsmoking cessation or other addictions. Some examples of current andfuture vaccines for the prevention of, anthrax, cervical cancer (humanpapillomavirus), dengue fever, diphtheria, Ebola, hepatitis A, hepatitisB, hepatitis C, haemophilus influenzae type b (Hib), HIV/AIDS, humanpapillomavirus (HPV), influenza (seasonal and pandemic), Japaneseencephalitis (JE), lyme disease, malaria, measles, meningococcal,monkeypox, mumps, pertussis, pneumococcal, polio, rabies, rotavirus,rubella, shingles (herpes zoster), smallpox, tetanus, typhoid,tuberculosis (TB), varicella (chickenpox), West Nile, and yellow fever.

In another embodiment, the substance of interest comprises a therapeuticagent. The therapeutic agent may be selected from small molecules andlarger biotechnology produced or purified molecules (e.g., peptides,proteins, DNA, RNA). Examples of therapeutics, which may include theiranalogues and antagonists, include but are not limited to insulin,insulin-like growth factor, insultropin, parathyroid hormone,pramlintide acetate, growth hormone release hormone, growth hormonerelease factor, mecasermin, Factor VIII, Factor IX, antithrombin III,protein C, protein S, β-gluco-cerebrosidase, alglucosidase-α,laronidase, idursulphase, galsulphase, agalsidase-β, α-1 proteinaseinhibitor, lactase, pancreatic enzymes, adenosine deaminase, pooledimmunoglobulins, human albumin, erythropoietin, darbepoetin-α,filgrastim, pegfilgrastim, sargramostim, oprelvekin, humanfollicle-stimulating hormone, human chorionic gonadotropin, lutropin-α,interferon (alpha, beta, gamma), aldesleukin, alteplase, reteplase,tenecteplase, urokinase, factor VIIa, drotrecogin-α, salmon calcitonin,exenatide, octreotide, dibotermin-α, recombinant human bone morphogenicprotein 7, histrelin acetate, palifermin, becaplermin, trypsin,nesiritide, botulinum toxin (types A and B), collagenase, humandeoxyribonuclease I, hyaluronidase, papain, 1-asparaginase,peg-asparaginase, rasburicase, lepirudin, bivalirudin, streptokinase,anistreplase, bevacizumab, cetuximab, panitumumab, alemtuzumab,rituximab, trastuzumab, abatacept, anakinra, adalimumab, etanercept,infliximab, alefacept, efalizuman, natalizumab, eculizumab,antithymocyte globulin, basiliximab, daclizumab, muromonab-CD3,omalizumab, palivizumab, enfuvirtide, abciximab, pegvisomant,crotalidene polyvalent fab (ovine), digoxin immune serum fab (ovine),ranibizumab, denileukin diftitox, ibritumomab tiuxetan, gemtuzumabozogamicin, tositumomab, I-tositumomab, anti-rhesus (rh) immunoglobulinG, desmopressin, vasopressin, deamino [Val4, D-Arg8] argininevasopressin, somatostatin, somatotropin, bradykinin, bleomycin sulfate,chymopapain, glucagon, epoprostenol, cholecystokinin, oxytocin,corticotropin, prostaglandin, pentigetide, thymosin alpha-1, alpha-1antitrypsin, fentanyl, lidocaine, epinephrine, sumatriptan, benztropinemesylate, liraglutide, fondaparinux, heparin, hydromorphone, omacetaxinemepesuccinate, pramlintide acetate, thyrotropin-alpha, glycopyrrolate,dihydroergotamine mesylate, Bortezomib, triptoreline pamaote,teduglutide, methylnaltrexone bromide, pasireotide, ondansetronhydrochloride, droperidol, triamcinolone (hex)acetonide, aripiprazole,estradiol valerate, morphine sulfate, olanzapine, methadonehydrochloride, and methotrexate.

In yet another embodiment, the substance of interest is a vitamin, herb,or dietary supplement known in the art. Non-limiting examples include5-HTP (5-hydroxytryptophan), acai berry, acetyl-L-carnitine, activatedcharcoal, aloe vera, alpha-lipoic acid, apple cider vinegar, arginine,ashitaba, ashwagandha, astaxanthin, barley, bee pollen, beta-alanine,beta-carotene, beta-glucans, biotin, bitter melon, black cherry, blackcohosh, black currant, black tea, branched-ahain amino acids, bromelain(bromelin), calcium, camphor, chamomile, chasteberry, chitosan,chlorella, chlorophyll, choline, chondroitin, chromium, cinnamon,citicoline, coconut water, coenzyme Q10, conjugated linoleic acid,cordyceps, cranberry, creatine, D-mannose, damiana, deer velvet, DHEA,DMSO, echinacea, EDTA, elderberry, emu Oil, evening primrose oil,fenugreek, feverfew, folic acid, forskolin, GABA (gamma-aminobutyricacid), gelatin, ginger, ginkgo biloba, ginseng, glycine, glucosamine,glucosamine sulfate, glutathione, gotu kola, grape seed extract, greencoffee, guarana, guggul, gymnema, hawthorn, hibiscus, holy basil, hornygoat weed, inulin, iron, krill oil, L-carnitine, L-citrulline,L-trypotophan, lactobacillus, magnesium, magnolia, milk thistle, MSM(methylsulfonylmethane), niacin, olive, omega-3 fatty acids, oolong tea,oregano, passionflower, pectin, phenylalanine, phosphatidylserine,potassium, probiotics, progesterone, quercetin, ribose, red yeast rice,reishi mushroom, resveratrol, rosehip, saffron, SAM-e, saw palmetto,schisandra, sea buckthorn, selenium, senna, slippery elm, St. John'swort, stinging nettle, tea tree oil, theanine, tribulus terrestris,turmeric (curcumin), tyrosine, valerian, vitamin A, vitamin B12, vitaminC, vitamin D, vitamin E, vitamin K, whey protein, witch hazel, xanthangum, xylitol, yohimbe, and zinc.

A microneedle patch may include a single substance of interest or it mayinclude two or more substances of interest. In the latter case, thedifferent substances may be provided together within one of themicroneedles, or some microneedles in an array of microneedles containone substance of interest while other microneedles contain anothersubstance of interest.

The API desirably is provided in a stable formulation or composition(i.e., one in which the biologically active material therein essentiallyretains its physical stability and/or chemical stability and/orbiological activity upon storage). Stability can be measured at aselected temperature for a selected period. Trend analysis can be usedto estimate an expected shelf life before a material has actually beenin storage for that time period.

In embodiments, the substance of interest is provided as a solid that is“dry” or has been “dried” to form the one or more microneedles andbecomes solubilized in vivo following insertion of the microneedle intothe patient's biological tissue. As used herein, the term “dry” or“dried” refers to a composition from which a substantial portion of anywater has been removed to produce a solid phase of the composition. Theterm does not require the complete absence of moisture (e.g., the APImay have a moisture content from about 0.1% by weight and about 25% byweight).

The substance of interest may be included in a formulation with one ormore excipients and other additives, as detailed below.

Matrix Material/Excipients

The matrix material forms the bulk of the microneedle, funnel portion,and backing layer. It typically includes a biocompatible polymericmaterial, alone or in combination with other materials. In embodiments,the matrix material, at least of the microneedles, is water soluble. Incertain preferred embodiments, the matrix material includes one or acombination of polyvinyl alcohol, dextran, carboxymethylcellulose,maltodextrin, sucrose and other sugars. As used herein, the terms“matrix material” and “excipient” are used interchangeably whenreferring to any excipients that are not volatilized during drying andformation of the microneedles, funnels, and base substrate.

The fluid solution used in the mold filling processes described hereinmay include any of a variety of excipients. The excipients may consistof those that are widely used in pharmaceutical formulations or onesthat are novel. In a preferred embodiment, the excipients are ones inFDA approved drug products (see the Inactive Ingredient Search forApproved Drug Products athttp://www.accessdata.fda.gov/scripts/cder/iig/index.Cfm). None, one, ormore than one excipient from the following categories of excipients maybe used: stabilizers, buffers, bulking agents or fillers, adjuvants,surfactants, disintegrants, antioxidants, solubilizers, lyo-protectants,antimicrobials, antiadherents, colors, lubricants, viscosity enhancer,glidants, preservatives, materials for prolonging or controllingdelivery (e.g., biodegradable polymers, gels, depot forming materials,and others). Also, a single excipient may perform more than oneformulation role. For example, a sugar may be used as a stabilizer and abulking agent or a buffer may be used to both buffer pH and protect theactive from oxidation. Some examples of excipients include, but are notlimited to lactose, sucrose, glucose, mannitol, sorbitol, trehalose,fructose, galactose, dextrose, xylitol, maltitol, raffinose, dextran,cyclodextrin, collagen, glycine, histidine, calcium carbonate, magnesiumstearate, serum albumin (human and/or animal sources), gelatin,chitosan, DNA, hylaruronic acid, polyvinylpyrrolidone, polyvinylalcohol, polylactic acid (PLA), polyglycolic acid (PGA), polylactiveco-glycolic acid (PLGA), polyethylene glycol (PEG, PEG 300, PEG 400, PEG600, PEG 3350, PEG 4000), cellulose, methylcellulose, carboxymethylcellulose, sodium carboxymethyl cellulose, hydroxypropylmethylcellulose, acacia, Lecithin, Polysorbate 20, Polysorbate 80,Pluronic F-68, Sorbitantrioleate (span 85), EDTA, hydroxypropylcellulose, sodium chloride, sodium phosphate, ammonium acetate,potassium phosphate, sodium citrate, sodium hydroxide, sodium carbonate,Tris base-65, Tris acetate, Tris HCl-65, citrate buffer, talc, silica,fats, methyl paraben, propyl paraben, selenium, vitamins (A, E, C,retinyl palmitate, and selenium), amino acids (methionine, cysteine,arginine), citric acid, sodium citrate, benzyl alcohol, chrlorbutanol,cresol, phenol, thimerosal, EDTA, acetone sodium bisulfate, ascorbylpalmitate, ascorbate, castor oil, cottonseed oil, alum, aluminumhydroxide, aluminum phosphate, calcium phosphate hydroxide, paraffinoil, squalene, Quil A, IL-1, IL-2, IL-12, Freund's complete adjuvant,Freund's incomplete adjuvant, killed Bordetella pertussis,Mycoobacterium bovis, and toxoids. The one or more selected excipientsmay be selected to improve the stability of the substance of interestduring drying and storage of the microneedle devices, as well providingbulk and/or mechanical properties to the microneedle array.

2. MICRONEEDLE PATCH

The microneedle array described above may be combined with one or moreother components to produce a microneedle patch, such as a patch thatcan be manually applied to the skin of a patient. For example, themicroneedle array may be combined with an adhesive layer, which may beused to facilitate securing the patch to a patient's skin during theperiod of administration of the substance of interest. A backing orhandle layer may further be included to facilitate handling of thepatch, as described above and illustrated in FIGS. 1 and 2.

The backing layer may be made out of a variety of materials, and may bethe same or different than the tab portion. In some embodiments, thebacking layer may be a composite material or multilayer materialincluding materials with various properties to provide the desiredproperties and functions. For example, the backing material may beflexible, semi-rigid, or rigid, depending on the particular application.As another example, the backing layer may be substantially impermeable,protecting the one or more microneedles (or other components) frommoisture, gases, and contaminants. Alternatively, the backing layer mayhave other degrees of permeability and/or porosity based on the desiredlevel of protection. Non-limiting examples of materials that may be usedfor the backing layer include various polymers, elastomers, foams,paper-based materials, foil-based materials, metallized films, andnon-woven and woven materials.

A microneedle patch may be stored in protective packaging prior to use.In one case, the microneedle patches are combined with a storage tray.One or more trays may be disposed in a flexible container (e.g., pouch)and/or rigid container (e.g., box). In some embodiments, a lid may bedisposed on the tray to protect the microneedle patch prior to use. Suchlids may be the same or a different material from the tray, and may besealed to the perimeter of the tray (i.e., using a heat seal, cold seal,or pressure sensitive adhesive). In one embodiment, a desiccant may beprovided in the recessed regions or in the flexible or rigid containerhousing the tray. A desiccant may alternatively or in addition be partof the tray itself. For example, a desiccant material may be included(e.g., dispersed in or coated onto) the material forming the structureof the tray. For example, the tray may be formed of a desiccant polymerknown in the art. The desiccant may be used to complete the drying ofthe microneedles after removal from the production mold.

In one embodiment, the microneedle patch includes an array of severalmicroneedles, e.g., from 10 to 1000 microneedles. In a preferredembodiment, the microneedles are solid microneedles that include asubstance of interest, such as an active pharmaceutical ingredient(API), which becomes solubilized in vivo following insertion of themicroneedle into a biological tissue, e.g., into the skin of a patient.For example, the substance of interest may be mixed into a water solublematrix material forming a solid microneedle extending from a basesubstrate. The substance of interest is provided in a formulationreferred to herein as being “dissolvable.” In embodiments in which thesubstance of interest and a matrix material in which the substance ofinterest is dispersed form the structure of the microneedle, the matrixmaterial also preferably is dissolvable in vivo, such that the entiremicroneedle dissolves in vivo.

In one embodiment, the microneedles within a given patch all contain thesame active and excipients. However, the actives and/or the excipientsmay be different in each microneedle, in different rows of microneedles,or sections/regions of the microneedle array. Possible reasons fordesigning the microneedle patch with such segregation are: i) thedifferent actives are incompatible with one another, ii) the differentactives require different stabilizing excipients, and iii) differentrelease profiles (e.g., combination of rapid bolus followed by asustained release) are desired of a single active or of differentactives. Examples are different arrays and patches are described inFIGS. 5-12.

3. METHOD OF MAKING MICRONEEDLE ARRAYS

Embodiments of the manufacturing methods described herein are used tomake microneedle arrays, which, generally described, include a basesubstrate with one or more microneedles extending from the basesubstrate. Generally speaking, the method includes a molding process,which advantageously is highly scalable. The process entails providing asuitable mold; filling the mold with suitable fluidized materials;drying the fluidized material to form the microneedles, the funnelportions if included, and the base substrate; and then removing theformed part from the mold. These filling and drying steps may bereferred to herein as “casting.”

FIG. 13 illustrates one embodiment of a molding process that includestwo castings. In this embodiment, a mold 1301 is provided and thenfilled with a first fluidized material 1302, followed by drying thefirst fluidized material 1302 thereby forming microneedles of amicroneedle array 1306. After which, the mold 1301 is filled with asecond fluidized material 1304, followed by drying the second fluidizedmaterial 1304 thereby forming a corresponding funnel portion for eachmicroneedle of the microneedle array 1306. The microneedle array 1306 isthen removed from the mold 1301. In a preferred embodiment, the firstfluidized material 1302 includes a drug or other substance of interest,and the second fluidized material 1304 does not include a drug or othersubstance of interest. A process flow diagram of one method of makingthe microneedle arrays as described herein is illustrated the block flowdiagram shown in FIG. 25.

In a preferred embodiment, a method is provided for making an array ofmicroneedles, which includes (a) providing a mold having an uppersurface, an opposed lower surface, and an opening in the upper surface,wherein the opening leads to a first cavity proximal to the uppersurface and to a second cavity below the first cavity, wherein the firstcavity defines a primary funnel portion, and wherein the second cavitydefines at least one microneedle; (b) filling at least the secondcavity, via the opening in the mold, with a first material whichcomprises a substance of interest dissolved or suspended in a firstliquid vehicle; (c) drying the first material in the mold to remove atleast a portion of the first liquid vehicle to form at least a tipportion of a microneedle in the second cavity, wherein the tip portioncomprises the substance of interest; (d) filling the first cavity, andthe second cavity if any is unoccupied following steps (b) and (c), viathe opening in the mold, with a second material which comprises a matrixmaterial dissolved or suspended in a second liquid vehicle; (e) dryingthe second material in the mold to remove at least a portion of thesecond liquid vehicle to form (i) a primary funnel portion, and (ii) anyportion of the at least one microneedle unformed following steps (b) and(c), wherein the primary funnel portion comprises the matrix material;and (f) removing from the mold the at least one microneedle togetherwith the primary funnel portion connected thereto, wherein more of thesubstance of interest is located in the at least one microneedle than islocated in the primary funnel portion. The matrix material in step (e)may further form a base substrate connected to the primary funnelportion distal to the at least one microneedle. In a preferredembodiment, the percentage of the substance of interest located in theat least one microneedle is at least 50%, more preferably 60%, morepreferably 70%, more preferably 80% and more preferably 90%. Typically,this percentage represents the average percentage among the microneedlesloaded with the substance of interest within a microneedle patch.

In another preferred embodiment, a method is provided for making anarray of microneedles, which includes (a) providing a non-porous andgas-permeable mold having an upper surface, an opposed lower surface,and a plurality of openings in the upper surface, wherein each openingleads to a cavity which defines a microneedle; (b) filling the cavities,via the openings, with a fluid material which comprises a substance ofinterest dissolved or suspended in a liquid vehicle; (c) drying thefluid material in the mold to remove at least a portion of the liquidvehicle and form a plurality of microneedles which comprise thesubstance of interest; and (d) removing the plurality of microneedlesfrom the mold, wherein the filling of step (b) is conducted with apressure differential applied between the upper and lower surfaces ofthe mold. This advantageously can enable filling, particularly ofviscous materials, at useful rates. For example, the pressuredifferential can be achieved by applying a pressure greater thanatmospheric to the upper surface, applying a pressure smaller thanatmospheric to the lower surface or a combination of both.

In another embodiment, a method is provided for making an array ofmicroneedles, which includes providing a two-part mold having a upperportion and a lower portion, the upper portion having an upper surface,an opposed lower surface, and an opening extending therethrough, theopening defining an upper cavity, the lower portion having an uppersurface, an opposed lower surface, and an opening in the upper surfacewhich is in fluid communication with the upper cavity and which leads toa lower cavity, the lower cavity defining a microneedle, wherein theupper portion and the lower portion are separably secured together;filling at least the lower cavity, via the opening in the upper portion,with a first material which comprises a substance of interest dissolvedor suspended in a first liquid vehicle; drying the first material in themold to remove at least a portion of the first liquid vehicle to form amicroneedle which comprises the substance of interest; and removing themicroneedle from the mold.

Methods for manufacturing microneedle arrays and patches preferably areperformed under a minimum ISO 5 (100) process, an ISO 7 process, or anISO 8 process. Terminal sterilization may be utilized when compatibilityof the sterilization method with the active has been demonstrated.

The Mold

In embodiments, the mold used to manufacture microneedle arrays containscavities that are the negative of the microneedles, and of any funnelportions, to be produced. In some embodiments, the mold includes afunnel section that is only used to increase the loading within themicroneedle and then is removed before processing the full microneedlearray. In those embodiments, the mold may be a two-part mold or includea separate filling template. Some of the novel methods of makingmicroneedles described herein may be used to make microneedles thatextend from a base substrate and do not include a funnel portion.

The molds can be formed from a single part or multiple parts. In oneembodiment, the two-part mold consists of a upper mold portion havingone or more cavities defining a funnel portion and a lower mold portionhaving one or more cavities defining one or more microneedles. The moldportions may be permanently or reversibly secured to one another. Moldsconsisting of two or more parts can be aligned and reversibly orirreversibly connected to one another by applying pressure (e.g.,pneumatic, mechanical force or clamp), adhesive, magnetic/electricalcharge, surface tension, chemical bonding (i.e., covalent,non-covalent), or vacuum.

Examples of various molds are illustrated in the cross-sectional viewsof FIGS. 14-16. FIG. 14 shows an embodiment of a single part mold 1400having an upper surface 1405 and a lower surface 1410. The upper surface1405 has openings 1415, wherein each opening 1415 leads to a firstcavity 1420 proximal to the upper surface 1405 and a second cavity 1425that extends from the first cavity 1420 in a direction away from theupper surface 1405. The first cavity 1420 defines a primary funnelportion 1430 and the second cavity 1425 defines a microneedle 1435.FIGS. 15 and 16 show embodiments of two-part molds. FIG. 15 shows oneembodiment of a two-part mold 1500 having an upper portion 1501separably secured to a lower portion 1502. The upper portion 1501includes an upper surface 1505, an opposed lower surface 1506, and anopening 1515 extending therethrough, wherein the opening 1515 defines anupper cavity 1520. The lower portion 1502 includes an upper surface1509, an opposed surface 1510, and openings 1522 in the upper surface1509. The openings 1522 are in fluid communication with the upper cavity1520, and each opening 1522 leads to a lower cavity 1525 that defines amicroneedle 1535.

FIG. 16 illustrates another embodiment of a two-part mold 1600 having anupper portion 1601 separably secured to a lower portion 1602. The upperportion 1601 includes an upper surface 1605, an opposed lower surface1606, and openings 1615 extending therethrough, wherein each opening1615 defines an upper cavity 1620. The lower portion 1602 includes anupper surface 1609, an opposed surface 1610, and openings 1622 in theupper surface 1609. Each opening 1622 is in fluid communication with acorresponding upper cavity 1620, and leads to a lower cavity 1625 thatdefines a microneedle 1635.

In one embodiment, the upper cavity serves as a filling cap during thefilling of the lower cavity. That is, the upper cavity is configured nota funnel but instead as a structure useful to keep the liquid materialin place over/above the opening during the drying process, at leastuntil the material is sufficiently solidified that it will not flowaway. The filling cap may be discarded after formation of themicroneedles.

The molds may be reusable or disposable. With traditional moldingprocesses, the molds are costly and are generally composed of hardenedsteel, which can be used over and over to create, for example, millionsof parts. Since the mold/tooling cost is spread out over many parts,that process is still economical. However, low-cost single-use molds arealso of interest. For example, molds made of elastomers manufactured bycasting or direct machining techniques (e.g., laser ablation) can beinexpensive to make. Also, their elastomeric properties allow themicroneedle arrays to be more gently removed from the molds versus rigidmold materials. Often disposable manufacturing tools are preferred inpharmaceutical and/or aseptic manufacturing because they have advantagesfrom a sterility and cleanliness perspective (e.g., no rigorous cleaningmethods or cleaning validations to ensure the active has been fullyremoved between manufacturing batches).

The geometries of the molds are generally the inverse of the microneedlearrays to be produced. The molds essentially have the same geometries(in inverse form) as the geometries described above for the microneedlesand funnels.

In general, the molds can be open (i.e., no top portions) for casting orsimilar type filling processing, or they can have separate top portionsthat are compatible with a pressure driven or injection molding typefilling process. The molds can be sized to produce an individualmicroneedle (i.e., single cavity), more than one microneedle array(i.e., multi-cavity) in the form of a sheet or plate, or multiple arraysof microneedles, which in turn can be assembled into patches. In onecase, the molds can be the form of a flexible roll that is fed through acontinuous reel-to-reel process, an embodiment of which is shown in FIG.19.

FIG. 19 is a cross-section view of one example of a system for use in acontinuous filling process. It shows part of a loop of flexible mold1901 which include spaced microneedle cavity arrays 1902. The mold 1901is fed by rollers, or reels, 1907 through a stationary filling stationthat includes pressure/fill head 1904. The pressure/fill head 1904includes a reservoir 1904 containing a fluid 1905 that, under pressure,is driven into the cavities of the arrays 1902. Stationary plate 1906contacts the back (“lower”) side of the mold 1901 and secures/stabilizesthe mold about the cavity array 1902 being filled, providing an opposingforce against the mold to provide a fluid tight interface between thepressure/fill head 1904 and the mold 1901. In embodiments, thestationary plate 1906 may be a vacuum plate, providing a pull force onthe bottom of the mold to complement the push force on the top of themold. The filled microneedle arrays are then moved to other positions,downstream, for further processing.

The mold may be manufactured from a variety of materials including, butnot limited to metals, polymers, ceramics, elastomers, composites, etc.or a combination of these or other materials. The molds may be solid,may contain discrete pores/voids, and/or may be permeable to gases buthave very low or no permeability to liquids, such as the processingsolvents (liquid vehicles) of interest. Examples of suitable processingsolvents include water and organics solvents, such as volatile organicsolvents known in the art of polymer molding.

In one embodiment, the mold is made of silicone (e.g.,polydimethylsiloxane, PDMS), which is permeable to air, but not verypermeable to water and other solvents. This enables the air to beremoved from microneedle/funnel cavities of the mold through the moldwalls via a pressure gradient from inside the mold cavities (high) tooutside the mold (low). This process advantageously is more scalable andsuited for an aseptic environment versus, for example, applying vacuumaround the entire system as described in the literature. The PDMSadvantageously does not contain discrete interconnected pores likeporous metal or porous ceramic molds. These discrete pores may becomeclogged with dried excipients causing them to be taken offline andreplaced and/or aggressively cleaned. The PDMS mold is also elastomeric,which beneficially provides for a very gentle demolding process thatdoes not require release agents/coatings, unlike rigid mold materials.Microneedle tips may break off in a mold during the demolding processwhen using rigid molds. This would produce inferior microneedles andwould require the molds to be aggressively cleaned before reuse. With asuitable elastomeric (e.g., PDMS) mold, the chance of microneedlebreaking is lower, and the molds can be manufactured inexpensivelyenabling them to be single-use molds, if desired.

In particular embodiments, the molds have much greater permeability toair than to water or other liquid solvents (such that they areconfigured/effective to enable the removal of air from molds duringmicroneedle manufacturing by a pressure gradient across the mold walls)and lack an interconnected porous structure. In particular embodiments,the molds are made of materials that are flexible/elastomeric (such thatthey are configured/effective to mold and demold without the use ofrelease agents/coatings, to effect demolding by deforming the mold,and/or to enable cost effective single use molds).

The molds preferably are made of materials that produce no or minimalleaching or dusting. The materials of construction of the molds areselected to be compatible with the substance of interest, excipients,disinfectants (e.g., ethanol, isopropanol), one or more commonsterilization methods (e.g., heat, steam, ethylene oxide, irradiation,chemical, UV light), and other processing materials used to form themicroneedle arrays.

In optional embodiments, the molds are coated with a material thatserves as a release agent so that the microneedle arrays/patches aremore easily removed from the mold. The molds may have ejection pins orsimilar mechanical structures to aid in microneedle array/patch removal.

In a preferred embodiment, the mold surfaces, e.g., the surfaces of thecavities in contact with and defining the microneedles and funnels,should be smooth. Minimal surface roughness aids with a cleaner fillingprocess (i.e., more active transferred to the microneedle and its tipversus the sidewalls of the funnels), demolding the microneedle patchfrom the mold, and reduces friction during microneedle insertion (i.e.,smooth-walled molds create smooth-walled microneedles that have lessfrictional losses during insertion than microneedles with roughsurfaces). The surface roughness average (Ra) should be less than 10microns, preferably less than 1 micron, and more preferably less than0.1 microns.

The molds may be made by grinding, milling (e.g., conventional milling,micromilling, nanomilling), drilling, laser processing (e.g., ablation,drilling), electrodischarge machining (e.g., EDM, microEDM), wet and/ordry etching, 3D printing, electroforming, lithography (e.g., UV,stereolithography), etc. In a preferred embodiment, the mold is formedby making a casting of a master structure. The master structure can bemachined using the techniques described herein or otherwise known in theart for mold manufacturing. The geometry of the master structure can bethe same geometries as the geometries described herein for themicroneedles.

Although the foregoing molds and molding casting processes may bedescribed with reference to manufacturing a single microneedle patch,the molds may be configured to form a plurality of microneedle patches.For example, in embodiments the mold may be configured to produce 6 ormore patches, 12 or more patches, and the like.

Filling

The composition of the filling solutions generally reflects the desiredmaterials in the final microneedle array, with the exception of thesolvents that may be substantially removed during the process.

In a preferred embodiment, the substance of interest is loadedpreferentially into the microneedles and their tips, and not into thefunnel portions. The substance of interest is part of a filling materialthat is transferred into the mold. The filling material may also includea liquid vehicle. The filling material may be in the form of a solution,slurry or suspension of particles, melt, powder or particles, or acombination of any of these forms. One or more of these forms may beused in a multi-step filling process. This “filling material” may bereferred to herein as a “solution” or as a “fluid material”.

In various filling steps, the filling material may include a liquidvehicle. The term “liquid vehicle” may be referred to herein as a“solvent” or a “carrier fluid.” In various embodiments, the fillingmaterial may include (1) only the solvent, (2) no solvent, (3) only amatrix material, (4) a combination of a solvent and a matrix materialwith no substance of interest, (5) a combination of only a solvent and asubstance of interest, or (6) a combination of a solvent, a substance ofinterest, and a matrix material. The solvent may be water, an organicsolvent, such as a volatile organic solvent, or a combination thereof.Some examples are Class 3 solvents that include acetic acid, heptane,acetone, isobutyl acetate, anisole, isopropyl acetate, 1-butanol, methylacetate, 2-butanol, 3-methyl-1-butanol, butyl acetate, methylethylketone, tert-butylmethyl ether, methylisobutyl ketone, dimethylsulfoxide, 2-methyl-1-propanol, ethanol, pentane, ethyl acetate,1-pentanol, ethyl ether, 1-propanol, ethyl formate, 2-propanol, formicacid, and propyl acetate.

The microneedle and funnel cavities may be completely filled, partiallyfilled, or overfilled. After a filling step occurs, it is generallyfollowed by a drying or curing step. The curing step can be achieved byheating or reduction in pressure (e.g., to evaporate solvent), bycooling or elevation of pressure (to solidify matrix material), exposureto light (e.g., polymerization due to ultraviolet light exposure) orcombinations of these. This drying or curing step may fully,substantially or only partially dry or cure the deposited material. Ingeneral, the solution transfers more of the active into the microneedleand their tips when its viscosity is low, it has high surface energywithin the funnel, and is not saturated with active (i.e., active ishighly soluble in the solvent). However, none of these threecharacteristics are required, they just typically enable morepreferential loading of the microneedles and their tips.

In a preferred embodiment, a two-step filling process is used, whereinthe first filling step contains the substance of interest, whichsubstantially migrates into the microneedle and its tip during thedrying/curing process. This is followed by a second filling step and asubsequent drying/curing process. This second filling step contains thematrix material(s) that give the microneedles and funnels theirmechanical structure and may be overfilled to create the base substrateor part of the base substrate.

In other embodiments, a single filling step or more than two fillingsteps may be used. A single filling step may be desirable, for example,if the active is inexpensive and the excess active in the funnel andbase can be wasted. More than two filling steps may be desirable tofurther increase the loading of the active in the microneedles above andbeyond the funnels' enhancement, further target the active within themicroneedles and their tips, deposit multiple actives or excipients indiscrete layers within the microneedles, deposit multiple actives orexcipients within different needles or sections of needles within agiven microneedle patch and/or impart further functionality into themicroneedle patch (e.g., insert a rapidly dissolving or fracturablelayer where the microneedles meet their funnels to allow for rapidseparation of the microneedles thereby significantly decreasing requiredadministration time).

One embodiment of a process that includes more than two-filling steps isas follows: The molds may be filled with a first solution containing anactive (as well as possible excipients), which is then dried. The moldis filled again with the same solution and dried. This can be repeateduntil the desired quantity of active is loaded into the microneedles.This is followed by one or more final filling steps in which the moldsare filled with excipients (which could be the same and or differentexcipients as in prior fillings) and without active, which provide themicroneedles with their mechanical structure once dried.

Another embodiment of a process that includes more than two-fillingsteps is as follows: Although the funnels allow for preferential fillingof the microneedles with active (as well as possible excipients), someof the active may deposit on the sidewalls of the funnels. This is morepronounced as the solutions become more viscous and/or supersaturatedduring the drying process. Therefore, one or more ‘rinsing’ steps may beinserted into the process that will carry the active further down intothe microneedles (i.e., towards the microneedle tips). The rinsing stepswill consist of a solvent or carrier for the active (as well as possibleexcipients) but containing no active. As the solvent or carrier fillsthe funnels, it redissolves or ‘picks up’ active and transports it intothe microneedle as it migrates into the microneedle cavity. This isfollowed by final filling step(s) in which the molds are filled with theexcipients (which could be the same and or different excipients as inprior fillings) and without active, which provide the microneedles withtheir mechanical structure once dried.

In one embodiment, the filling process includes a first filling whichuses a volume of solution that is substantially equal to or less thanthe volume of the microneedle plus the funnel cavity and preferablygreater than the volume of the microneedle cavity. This filling processis most amenable to filling with droplets of the specified volume. Themicroneedle+funnel volume is the sum of the volume(s) of the microneedlecavity(ies) that are all being filled at that time during the fillingprocess and the volume(s) of the funnel(s) that are connected to thesemicroneedle cavity(ies) being filled. In one embodiment, the fillingprocess includes a second filling which uses a volume of solution thatis substantially equal to or greater than the volume of themicroneedle+funnel cavity. The filling process may combine these firstand second filling steps as described above in this paragraph.

In embodiments, the filling step includes one or more features orsub-steps that enhance preferential loading of the fluid or thesubstance of interest into the microneedles versus the funnel portions.Combinations of the following embodiments are envisioned.

In one embodiment, the funnel portion is provided with a relativelysteep funnel angle. By having a steeper funnel angle, it allows forgravity (or an applied pressure gradient) to further influence flow ofthe solution down (i.e., towards the microneedle tips) the sidewalls ofthe mold as it is drying. For this reason, microneedle and moldgeometries may include steep funnel angles. Here and elsewhere in thisdisclosure reference to movement “down” does not necessarily refer to anorientation relative to gravity, but refers to an orientation relativeto the mold, such that “down” refers to movement toward the microneedletip.

In one embodiment, at least the funnel portion of the mold cavity isprovided with smooth sidewalls. By having smooth sidewalls, it helps thesolution migrate into the microneedles as it dries. The solution is lesslikely to become caught in cracks and crevices, and it will have lessfrictional resistance to flow driven by gravity, surface tension,pressure-driven convection, vibration, electrophoresis/electroosmosisand other forces.

In one embodiment, the microneedle portion of the mold is provided witha lower surface tension than in the funnel portion. By having arelatively higher surface tension in the funnel portion and a relativelylower surface tension in the microneedle portion of the mold, thesolution will more easily and cleanly migrate down the funnel and intothe microneedle portion of the mold. Surface tension can be influencedby both the solution properties and the mold surface. Accordingly, thesurface tension may be altered by selection and use of surfactants,oils, mold surface roughness, coatings, etc.

In one embodiment, the filling solution is provided to have a lowviscosity. A fill solution having a relatively low viscosity is morefluid and as it dries it can more easily flow down into themicroneedles. In embodiments in which the solution includes the active,it is generally preferred that the viscosity of the solution be lessthan about 100 cp, more preferably less than about 50 cP, morepreferably less than about 10 cP, or more preferably less than about 5cP.

In a particularly useful and preferred embodiment, the filling processincludes a rinse step. This “rinse down” or “rinse” step may be used tofurther preferentially load the microneedles and their tips. In a rinsestep, after filling with the active and drying/curing, the molds may berefilled with a solvent/carrier to redissolve or pick up the active andcarry it down into the microneedle cavities where it can resettle. Therinse down step rinses active off the walls of the funnel and transfersit into the microneedle. Therefore, in one embodiment, the moldingprocess includes at least three casting processes in the followingorder: a casting process that deposits active in the mold, a castingprocess that “rinses” active further down into the mold (i.e., with theobjective of removing active from the funnel portion of the mold andmoving it into the microneedle portion and/or tip of the microneedleportion of the mold), a casting process that deposits excipient(s) whichprovide the microneedles with their mechanical structure once dried.

In one embodiment, vibration or ultrasound is applied to the mold tofacilitate movement of the active move downward from the funnel andtoward the microneedle during drying. The vibration will help more ofthe solution/active find the point of lowest energy in the mold (i.e.,microneedles and their tips).

In one embodiment, the filling step includes application of anelectromagnetic field, or a combination thereof, to the fillingmaterial. For example, electrophoresis, electroosmosis, magnetophoresis,or other mechanisms mediated by electric and magnetic fields may beused.

In one embodiment, a pressure is applied to the fluid to further aidmigration of the solution towards and into the microneedle cavities. Thepressure can be applied in the form of flowing sterile air/nitrogen(i.e., a blower) or similar methods for creating a pressure gradient tohelp drive the solution down as it dries.

In one embodiment, a vacuum is applied to the bottom side of the mold,wherein the mold includes discrete pores or wherein the mold ispermeable to air. Such a vacuum can help pull the solution down into themicroneedle cavities as it dries.

In one embodiment, a positive pressure is applied to the top side of themold, wherein the mold includes discrete pores or wherein the mold ispermeable to air. Such a positive pressure can help push the solutiondown into the microneedle cavities as it dries.

In one embodiment, a centrifuge or similar device is used to spin themolds to create a force normal and into the molds, creating agravitational force to drive the solution down into the microneedles asit dries/cures. This process also can useful be to drive largermolecules (e.g., the active) down into the microneedles and their tipswhile the filling fluid is still in the solution state. The term “largermolecules” is used to mean molecules that are larger than those of theliquid vehicle, or solvent, and can also include nanoparticles,microparticles and other particles made up of many molecules.

In various embodiments, the microneedle molding process includes one ormore of the following steps before, during and/or after any or all ofthe mold filling steps: application of vibration, ultrasound, pressure,vacuum, an electromagnetic field, and centrifugation.

In one embodiment, precipitation of the active is controlled to occur inthe microneedle and not in the funnel portion. By keeping the active insolution when the solution is still in the funnel will result in lessactive depositing onto the side walls of the funnel. To do this, themolds need to be filled with a solution that is not saturated withactive. The solution should approach saturation as it dries to the pointof only occupying the volume of the microneedle cavities. At this pointthe active will fall out of solution and migrate further into themicroneedle cavities.

A variety of methods may be used to fill the molds. Examples includeblanketing the entire area of the microneedle patch and/or fillingindividual funnels directly.

The microneedle cavities within a mold are closed at their tips. If asolution is cast on top of the entire mold or funnel, etc. air willremain within the microneedle/funnel cavity. This air needs to beremoved in order to fill the molds with material and correctly replicatethe microneedles. A variety of methods can be used to remove this air,including, but not limited to; 1) filling with solution under vacuum(i.e., no air is in the microneedle/funnel cavities to begin with), 2)applying vacuum after depositing the solution, which will cause theentrapped air to expand and rise up through and out of the solution, 3)applying a pressure gradient across a mold that is permeable to air(e.g., vacuum from the underside of the mold, pressure to the top sideof the mold, or both) so that the air is expelled through the molditself, 4) subjecting the molds to centrifugation to drive the solutioninto the molds, 5) using sonication or other physical methods from thebottom-side or top-side of the mold to expel air bubbles from the moldcavities, and/or 5) a combination of these methods.

Microneedle-by-microneedle filling is difficult using conventionalmicroneedle molds due to the small target size (e.g., leads tomisalignment and missing the individual microneedle reservoirs in themold) and small volume that needs to be deposited (e.g., extremely smalldeposition volumes will lead to increased variation in the volumedeposited). This becomes increasingly difficult in high-volumemanufacturing. However, funnel-to-funnel (i.e., depositing fillingmaterials into individual funnel mold cavities) and ‘blanket’ filling(i.e., covering areas of the mold surface that include multipleindividual microneedle/funnel mold cavities) is much easier because thetarget area can be many times larger than the opening area of anindividual microneedle cavity. With funnel-to-funnel filling, the fillvolume (i.e., volume of microneedles and funnels) and targeted area(i.e., area of funnel-base interface) advantageously are many timeslarger than the fill volume and target area of a microneedle alone, sothis can greatly reduce variation in the volume deposited (e.g., 5 nl±1nl is 5 nl±20% and 100 nl±1 nl is 100 nl±1%—a 20-fold difference in theabsolute variation in this scenario) and drop-to-target misalignments.With blanket filling, the entire area is covered with solution therebyfurther reducing the volume and positional constraints. The volumedeposited via the blanketing method can be less than, equal to, orgreater than the combined volume of the microneedles and funnels. Anyexcess solution is removed (e.g., wiped, air purged) once themicroneedle and funnel cavities are filled.

The volume of solution deposited into the microneedle molds may becontrolled by the volume of the cavities within a mold (i.e., completelyfill cavity with solution and then clean surface) or the filler (i.e.,dispense or load controlled volume, mass, etc.). For microneedle arraysproduced by multiple filling steps, these volume control methods mayboth be used. For example, the solution containing the active is blanketcoated over the entire surface, the microneedle and funnel cavities arefilled, the solution is cleaned from the surface of the mold, thesolution is dried, a second solution is deposited in a controlled amountby a filler, the second solution is dried, etc.

When filling a microneedle mold that does not have funnels, the amountof an active deposited in the microneedle is equal to the volume of themicroneedle mold cavity multiplied by the concentration of the active inthe filling solution. Increasing the amount of active in the microneedlecan be achieved by increasing the concentration of the active in thefilling solution. This will be limited by solubility, suspendability andother factors. Increasing the amount of active in the microneedle can beachieved by increasing microneedle mold cavity volume. This will belimited by how large the microneedle can be and still achieve itsintended function, e.g., insertion into skin or other tissue, painlessapplication etc. The addition of a funnel to the microneedle mold designeffectively advantageously increases the volume of the microneedle moldduring filling without changing the volume of the microneedle itselfduring use. This is because the microneedle and funnel portions of themold can be filled together and, due to manufacturing process design,the materials dissolved, suspended or otherwise associated with thefilling solution can be preferentially deposited in the microneedleportion of the mold upon drying. However, when the microneedle patch isapplied to the skin or other tissue, only the microneedle portionsubstantially penetrates into the skin, whereas the funnel portion doesnot substantially penetrate into the skin, making it effectively part ofthe base portion of the patch.

Accordingly, microneedle arrays are provided herein that contain anamount of active in the microneedles (termed quantity A) (and/oradminister an amount of active from the microneedle, termed quantity A′)that is greater than the total volume of microneedles in the patchmultiplied by the average concentration of the active in the fillingsolution during each of the one or more fillings employed duringmanufacturing multiplied by the number of fillings employed duringmanufacturing (termed quantity B). Conventional microneedle mold filling(without funnels) cannot achieve this amount of active (i.e., typicallyA or A′≤B). The use of funnels enables us to achieve this amount ofactive (A or A′≥B). For example, A or A′≥1.5 B; or A or A′≥2 B; or A orA′≥3 B; or A or A′≥5 B.

During blanket filling or other methods that do not place fillingsolution exclusively in mold cavities, there can be loss of fillingsolution left on the mold surface. During methods that intend to placefilling solution exclusively in mold cavities, there can be loss offilling solution on the mold surface because of inaccuracies in thefilling process that do not successfully place filling solutionexclusively in mold cavities. Having larger areas at the top of the moldcavities makes exclusively filling the mold cavities easier to do,because deposition methods will be able to more easily selectivelydeposit material in mold cavities that have larger openings. The use offunnels allows that mold cavity opening to be larger than the base ofthe microneedle. The base of the microneedle using conventional moldsthat do not include funnels is at the interface of the microneedle andthe base of the mold. Thus, the base of the microneedle defines the sizeof the opening of the mold cavity. In contrast, the base of themicroneedle using molds that include funnels is at the interface of themicroneedle and the funnel, and the size of the opening of the moldcavity is at the interface of the funnel and the base of the mold. Inthis way, the size of the base of the microneedle and the size of theopening of the mold cavity can be at least partially dissociated. Thegeometries of these interfaces are described above in the section ofgeometry of microneedles and of molds.

In another embodiment, methods of making microneedle arrays are providedin which one or more of the filling solution(s) are applied to the moldsuch that substantially all of the filling solution is deposited in themold cavities (i.e., within the funnel and microneedle portions of themold) and almost none of the filling solution is deposited on the moldsurface. The ability to have this selective deposition of the fillingsolution is enabled by having large mold cavity openings enabled by theuse of funnels. More specifically, the inclusion of a funnel portionenables methods in which the ratio of the amount of one or more activesdeposited in the mold cavities (i.e., within the funnel and microneedleportions of the mold) to the amount deposited onto the mold is ≥80%,more preferably ≥90%, more preferably ≥95%, more preferably ≥98%, morepreferably ≥99%. In embodiments, the ratio of the amount of one or moreactives within the funnel and microneedle portions of the patch to theamount found in the whole patch (i.e., including the backing) is ≥80%,more preferably ≥90%, more preferably ≥95%, more preferably ≥98%, morepreferably ≥99%.

In embodiments, methods are provided to make microneedle patches inwhich each microneedle cavity is filled by separate filling-solutiondroplets (in parallel and/or in series) and where the droplets have avolume larger than the volume of the microneedle (i.e., the microneedleportion of the mold). The absolute volumes of the filling solutiondroplets may be the same as the volumes identified above for thecombined volumes of the microneedle and funnel portions of microneedlepatches and molds. Ratios of the microneedle volume (i.e., volume of themicroneedle in the microneedle patch or volume of the microneedleportion of the mold) to the droplet volume may be equal to the ratio ofthe microneedle volume to the sum of the microneedle and funnel volumes(or the sum of the microneedle and funnel portions of the mold)described above. More specifically, ratios of droplet volume tomicroneedle volume may be >1, more preferably ≥1.5, more preferably ≥2,more preferably ≥3, more preferably ≥5. The “droplet volume” may beconsidered to be the sum of the volume of multiple droplets applied tothe same mold cavity before substantial drying occurs, since it islikely that the fill of each mold cavity will not be with a single dropbut with multiple drops.

Other filling methods may be used to provide selective filling within apatch and within a needle including: applying localized and selectivepressure gradients to only fill the desired locations, varying thesurface properties (e.g., surface tension, specific and non-specificbinding site) of the mold in order to selectively fill the desiredlocations, in the case of filling with microchannels, the microchannelscould be divided only to cover and fill the desired portions of a patchor multiple solutions could be used that are either non-miscible ormiscible, but under low Reynolds Number flow (little or no mixing) tofill only the desired locations.

In one embodiment, a fluid handling/dispensing technology/system knownin the art to be capable of depositing solutions onto the molds is used.Some are suited for ‘blanket’ coating (regional or full patch), targeteddeposition, or both. A few examples of fluid handling/dispensing systemsare: syringe or other pumps coupled with dispensing heads (Tecan/Cavro,Gilson, Hamilton), automated pipetting systems (Tecan, Biotek,Eppendorf), screen printing or other mask and clean type systems, slotcoating or similar systems, inkjet printing systems (MicroFab), pin orcapillary array dispensing technologies, active capillary systems(Nanodrop by Innovadyne), aerosol or spraying based systems, dipping,brushing, stamping, surface chemistry controlled deposition(PRINT—Particle Replication In Non-wetting Templates), acoustic basedsystems (Picoliter, Inc.), and any combination of these depositiontechnologies (e.g., BioJet by BioDot, a syringe pump-inkjet hybrid). Thefilling heads may be automated and move, the molds may move, or both maymove, in order to deposit the solutions in the desired locations. Thismay be in the form of single-cavity molds, multi-cavity mold plates, oron a continuous reel-to-reel process. We disclose methods of fillingmicroneedle molds in which all the microneedle cavities and funnels arefilling at substantially the same time or in which different microneedlecavities and funnels are filled at different times. This can beaccomplished using droplets of filling solution applied selectively toindividual or subsets of microneedle cavities and funnels. This can beaccomplished by “blanket” filling of selected regions of the mold.

In one embodiment, vacuum filling is used. Vacuum can be applied beforedepositing the solution onto the molds. This removes the majority of theair prior to filling the mold. Also, vacuum can be applied afterdepositing the solution onto the mold. This removes the air from thecavities by causing it to expand and rise up through the depositedsolution and out of the mold. The vacuum can be applied to the wholemold or to selected regions of the mold, to flow through a gaspermeable/porous mold or both. such as the topside or the underside or asubset of microneedle cavities and funnels, such as to selectively fillthose microneedle cavities and molds with filling solution(s).

In a particularly preferred embodiment, filling of molds is carried outby applying vacuum through a gas permeable mold. For example, the vacuumcan be applied exclusively to the underside of the mold, so as to createa pressure differential across the mold (e.g., between the upper, opensurface of the mold and the opposed lower closed surface of the mold).One example of a vacuum apparatus for implementing such vacuum fillingis shown in FIG. 18, which shows vacuum plate 1800 having an uppersurface on which a gas-permeable mold 1802 is placed in mating on itsbottom side with a gas permeable/porous surface of the vacuum plate,thereby pulling the vacuum through the mold. The upper surface of themold has an array of openings into microneedle shaped cavities. By usinga mold that has discrete pores/openings or a mold that is solid, buthighly permeable to gases (air, nitrogen, etc.), the microneedle/funnelreservoirs can be filled simply by covering the opening of a funnel,multiple funnels, or an entire mold with the solution and then applyingvacuum from the underside of the mold. This pulls the air out throughthe mold and creates a pressure gradient to pull the solution into thecavities. See Example 8. Such a process advantageously can eliminate atransfer step for placing the entire mold into a vacuum chamber.

The mold used in this process can be made of any suitable gas permeablematerial, which is substantially impermeable to liquids. It preferablyis a non-porous material, having no interconnected pores in which solidscan become trapped. In a preferred embodiment, the mold is made of anelastomeric material such as silicone, e.g., polydimethylsiloxane.

It has been discovered that the time to remove the air and fill the moldwith solution is not strongly influenced by the solution viscosity, soit works well with both low viscosity and high viscosity solutions. Thefill time may for example be two to four minutes using this method. Thevacuum process advantageously is highly scalable because it can be donein parallel.

In another particularly preferred embodiment, which optionally may beused in combination with the preceding vacuum filling embodiment, thefilling of a gas permeable mold is carried out by applying an overpressure to the solution at the upper side (the cavity opening side ofthe mold). By injecting the solution into the mold or mold cavity withpressure, the air can be forced out through the mold itself, if the moldhas discrete pores/voids or is a solid mold made of a material (e.g.,silicone/PDMS) that is permeable or highly permeable to gases, but notvery permeable to liquids. For example, applying modest amounts ofpressure (65 psi, i.e., pressure differential of ˜50 psi) to thesolution has been shown to force the solution down into the cavities andair out through the PDMS mold or into the solution itself within 20seconds. The time to fill the molds with solution is not stronglyinfluenced by viscosity. See Example 9. This can be done by pressurizinga chamber above the mold. This chamber can be pressurized by a gasdirectly, or via a gas moving a barrier material (e.g., a piston ormembrane) to apply pressure directly to the solution. The pressure mayalso be applied similar to a traditional injection molding type process.The pressure may be applied mechanically by pressing on a movablebarrier (e.g., a piston or membrane) or directly on the solution itselfin the form of a plate or roller.

Therefore, in certain embodiments, filling of molds is performed byapplying pressure to the topside of a mold, which may consist ofapplying pressure exclusively to the topside of the mold. In otherembodiments, filling of molds is performed by applying vacuumexclusively to the underside of the mold. In other embodiments, fillingof molds is performed by a combination of applying pressure to thetopside of a mold and applying vacuum to the underside of the mold.Pressure gradients applied may be between 1 and 1000 psi and preferablybetween 10 and 100 psi.

The terms “pressure differential” and “pressure gradient” may be usedinterchangeably herein. The terms refer to the a difference in pressureused to create a driving force through the at least part of a thicknessof a mold, by the creation of a sub- or super-atmospheric pressure on anupper or lower side of the mold, such as for example by the use of apump. This “pressure differential” does not include intrinsic smalldifferences in atmospheric pressure or fluid pressure, caused bygravity, by virtue of the upper surface of the mold being positionedabove the lower surface of the mold or a head of fluid (e.g., castingsolution) being on top of the mold.

In one embodiment, direct droplet deposition is used to carry out thefilling of the molds. By depositing small drops via inkjetting or othertechnology, aerosols, or narrow fluid streams, the microneedle andfunnels can be filled directly without the need for external pressure orvacuum to be supplied, since they are able to fill themicroneedle/funnel cavity from the bottom up (i.e., microneedle tip upthrough the funnel-base interface and beyond). The droplets or streamsare on the size scale that is significantly less than the size scale ofthe microneedle/funnel cavities (i.e., drop/stream width to cavitywidth) all on a size scale that is significantly less than size of themold cavities). It may be difficult to administer droplets tomicroneedle molds without funnels, because droplets from depositionapparati may be larger than the microneedle-base interface width. Thisis an advantage of using funnels, in which the width of the funnel-baseinterface is larger than the width of the microneedle-funnel interface.The use of the funnel allows larger droplets to be used. Therefore, inone embodiment, the process of manufacture includes filling molds withdroplets that have a width that is smaller than the width of thefunnel-mold interface, and possibly larger than the width of thefunnel-microneedle interface, or that have a width that is smaller thanthe width of the funnel-microneedle interface.

In another embodiment, a method for filling includes placing discretecapping structures, thin film microcapillaries, and/or semi-continuoussurface microchannels onto the molds, filling them with solution, andthen filling the microneedle/funnel cavities by using a pressuregradient. The pressure gradient can be supplied as already described(i.e., applying vacuum from the underside of the mold and/orpressurizing the solution within the cap/channel). See Example 6.Solution can flow through these structures by other mechanism as well,such as capillary flow, electroosmosis and/or other mechanisms known inthe art of microfluidics. In such embodiments, filling of themicroneedle mold cavities uses a filling solution applied from the sideof the mold that flows in a direction substantially perpendicular to thecentral axis of the cavity. This contrasts with conventional fillingmethods that fill microneedle mold cavities with filling solutionsapplied from above the molds, flowing (through air) in a directionsubstantially parallel to the central axis of the cavity.

In one embodiment, a custom filling head is brought into contact andmakes a fluidic seal with the open side of the mold whereby a pressuregradient is added to drive and/or pull the solution into the mold. Thefilling head contains a solution reservoir that may contain a volumethat is equal to, greater than, and preferable much greater than themicroneedle/funnel mold cavities to be filled. The reservoir may also berefillable in-process, refillable outside of the process (e.g., removeit, fill it, reinstall it), or disposable, where it or it and thefilling head is (are) replaced with a new unit that is full. The fillinghead may be a tube with a thin and/or rounded edge, or may have ando-ring, gasket, or other sealing material so it can make sufficientcontact with the mold to make a fluid seal. The filling head may alsohave a porous material on its front face, where the porosity (pore sizeand number) and surface chemistry is controlled so that it does notdispense solution without an applied pressure gradient. The filling headmay be slid to the next microneedle array(s) (e.g., keeping its fluidicseal, face seal) or the solution may be retracted and the filling headmay be lifted off the mold and repositioned onto the next microneedlearray(s). A filling system and method may utilize more than one fillinghead. The filling head may be an elongated slot or some other geometryother than tubular that is more suitable for depositing the solutiononto many microneedle patch cavities simultaneously. In an embodiment,the face seal filling head beneficially removes excess solution from theface of the mold over the filled cavities.

FIG. 27 illustrates one embodiment of a system and filling method whichincludes the use of a filling head. System 2700 includes a gas permeablemold 2704 having three microneedle cavity arrays 2708 a, 2708 b, and2708 c (shown with each array having three microneedle cavities) whereineach array has openings on upper surface 2705 of the mold 2704. Afilling head 2702 contains filling material 2706 and mates against theupper surface 2705 of the mold 2704 and is shown in position fillingmicroneedle cavity array 2708 b. The horizontal arrows illustrate themovement of the filling head 2702 across the upper surface 2705 of themold 2704 to sequentially fill the cavity arrays with filling material2706, typically with aid of a pressure differential across mold (i.e.,pressure assisted and/or vacuum assisted).

Another way to expel air from the mold cavities and allow the depositedsolution to enter is to apply physical energy to the mold to displacethe air bubble up through or into the solution. For example, sonicationmay be applied from the bottom-side of the mold to expel the air fromthe cavities or it may be applied on the top-side of the mold and withinthe solution used to fill the cavities. Also, impact could be appliedfrom the bottom-side of the mold to expel the air from the cavity. Orstretching an elastomeric mold may be used to expel the air. Bystretching the elastic mold, the cavities can be closed down, therebydisplacing the air, the solution can be applied, the mold is allowed toreturn to its original state, and the cavities fill with solution.

A sponge (e.g., foam, fabric, or other absorbent material) filling headmay be used to fill the molds by pressing a saturated or partiallysaturated (with filling solution) filling head against themicroneedle/funnel cavities. The filling head(s) may be pressed againstthe mold and held in place one time or many times. When the spongecontaining the deposition solution is pressed against mold it isdeformed and expels solution that is forced (e.g., by pressure) into themicroneedle/funnel cavities, thereby filling and pushing out air fromthe cavities through the mold walls. After fill, the force is released,the sponge relaxes and then can be used to ‘mop’ or clean the surface ofany residual solution. There can be more than one sponge filling head.The sponge filling head may also be in the form of a roller. The spongefilling heads may be replenished with solution in-process by dispensingsolution onto them. Or a portion of the sponge may be in contact with asupply reservoir at all times so its solution saturation level remainsrelatively constant.

Drying

A number of drying and/or curing methods can be used throughout themanufacturing process. Heat may be applied in the form of a batchprocess, but it may be preferred to be integrated into a semi-batch orcontinuous process. Some of the drying methods, which harden thesolution by removing the solvent via evaporation, include theapplication of: 1) heat—through convection, conduction (i.e., hot plateor heated surface), and/or radiation (heat lamp, IR or NIR light), 2)convection—dry, desiccated, sterile air or nitrogen blower, 3)vacuum—exposure to reduced pressure, 4) ambient drying, 5) desiccation,6) lyophilization or freeze drying, 7) dielectric drying (e.g., rf ormicrowaves), 8) supercritical drying, and 7) a combination of one ormore drying methods.

A number of the curing methods (hardening of the substance results frompolymerization/cross-linking or reversible polymerization/cross-linkingof polymer chains) are brought about by electron beams, heat, orchemical additives/reactions. Curing triggers may include timeultraviolet radiation (e.g., UV light), pressure, heat, etc.

In an embodiment, the aqueous solution may be dried at ambienttemperature for a period from about 30 minutes to about one week to formthe dry solid microneedles (e.g., from about 45 minutes to about oneweek, from about one hour to about one week, from about one hour toabout one day, etc.). In one embodiment, the aqueous solution may bevacuum-dried using a backside vacuum for a period from about 3 minutesto about 6 hours, from about 3 minutes to about 3 hours, from about 3minutes to about 1 hour, or from about 3 minutes to about 30 minutes.Although various temperatures and humidity levels can be employed to drythe aqueous solution, the formulations preferably are dried attemperature from 1° C. to 60° C. (e.g., from 15° C. to about 45° C.,from about 25° C. to about 45° C., or at about ambient temperature) and0 to 40%, 0 to 20%, 0 to 10% or at ambient relative humidity.

As used herein, the term “drying,” “dried, or “dry” as it refers to thematerial in the mold (e.g., the matrix material and/or the substance ofinterest) refers to the material becoming at least partially solidified.In embodiments, the microneedles may be removed from the mold beforebeing fully dried. In one embodiment, the microneedles are removed fromthe mold after the microneedles are dried to be an operational state.However, in a preferred embodiment, the microneedles are removed fromthe mold when the microneedles are in a rubbery state but strong enoughto be pulled or peeled out of the mold. This has been found to improvedemolding without microneedle breakage. As used herein, the term“operational state” means that the microneedles are sufficiently rigidto be used for their intended purpose, e.g., to penetrate skin. As usedherein the term “rubbery state” means that the microneedles are not inan operational state, as they are too soft and flexible to penetratetheir intended target tissue, e.g., skin. For example, a microneedle,such as one comprised of a bulk/matrix material including polyvinylalcohol and a sugar, would, when undergoing a drying process, enter arubbery state, as its moisture content is reduced, before entering theoperational state.

De-Molding the Cast Product

The microneedle patches can be removed from the molds using a variety ofmethods. Non-limiting examples include 1) affixing an adhesive pad orbacking to the backside of the microneedle array and demolding andassembled microneedle patch from the mold, 2) removing the microneedlearray from the mold and affixing it to the adhesive pad or backing usingpick-n-place automation techniques (picked up by suction cup or smallgrippers), 3) ejecting from the molds using ejector pin or othermechanical technique that is similar to traditional injection moldingprocesses.

Additional Process Steps

In embodiments, a microneedle patch is composed of a first portion ofthe patch that is made using a mold-filling method and a second portionof the patch that is not made using the same mold-filling method. Inparticular, the second portion of the patch may be made before the firstportion of the patch is made. The second portion of the patch may becombined with the first portion of the patch at some point during orafter the mold-filling process used to make the first portion of thepatch. The first portion of the patch could be the microneedle, funneland base, and contain one or more actives. The second portion of thepatch could be a backing that is affixed to the topside of the moldedbase.

The microneedle patches may be inspected prior to packaging to ensurethat they meet their specifications. The machine vision industry hasdeveloped a number of technologies that can be adapted for this purpose.A number of inline and non-contact automated inspection systems (digitalinspection scopes (Keyence), chromatic confocal imaging (Nanovea), andreflection based systems) can be used.

The patches that meet their specification are then packaged. In apreferred embodiment, the package protects the microneedle patch and itscontents (i.e., active(s)) from mechanical damage, moisture, light,oxygen, and/or contamination (e.g., particulate, microbial). A singlemicroneedle patch may be affixed to a cap or multiple microneedlepatches may be affixed to a tray. The cap or tray may be made formedfrom plastic, metal (aluminum), metallized plastic, or other material.Examples of such microneedle patch caps and trays are described in PCTPatent Application Publication No. WO/2015/048777 to Georgia TechResearch Corporation.

4. METHODS OF USING THE MICRONEEDLE ARRAYS

The microneedle arrays and patches provided herein may beself-administered or administered by another individual (e.g., a parent,guardian, minimally trained healthcare worker, expertly trainedhealthcare worker, and/or others). Unlike prior art microneedle systems,the microneedle patches provided herein may be directly handled andadministered by the person applying the patch without requiring use ofan applicator to apply the required force/pressure, thereby allowing fora very simple, low-profile (i.e., thin and patch-like) microneedle patch(e.g., the total patch thickness, including any application aids, doesnot exceed 2 cm, more preferably 1.5 cm, more preferably 1 cm, and morepreferably 0.5 cm).

Thus, embodiments provided herein further include a simple and effectivemethod of administering a substance of interest with a microneedlepatch. The method may include identifying an application site and,preferably, sanitizing the area prior to application of the microneedlepatch (e.g., using an alcohol wipe). If needed, the application site maybe allowed to dry before application of the microneedle patch. The patchthen is applied to the patient's skin/tissue and manually pressed intothe patient's skin/tissue (e.g., using the thumb or finger) by applyinga sufficient pressure to insert the one or more microneedles into thepatient's skin/tissue. After administration is complete, the patch maybe removed from the patient's skin/tissue by manually grasping a tabportion (e.g., between the thumb and finger), peeling the patch off thepatient's skin/tissue, and discarding the patch.

In embodiments, the microneedle patches described herein are used todeliver one or more substances of interest (e.g., vaccines,therapeutics, vitamins) into the body, tissue, cells, and/or organ. Inone embodiment, the microneedles are used to deliver the active intoskin by inserting the microneedles across the stratum corneum (outer 10to 20 microns of skin that is the barrier to transdermal transport) andinto the viable epidermis and dermis. The small size of the microneedlesenables them to cause little to no pain and target the intradermalspace. The intradermal space is highly vascularized and rich in immunecells and provides an attractive path to administer both vaccines andtherapeutics. The microneedles are preferably dissolvable and once inthe intradermal space they dissolve within the interstitial fluid andrelease the active into the skin. Once the microneedles are fullydissolved, which generally takes a few minutes (e.g., <20 minutes), thepatch can be removed and discarded as non-sharps waste since themicroneedles dissolve away. The microneedles can be altered to providefor more rapid release or quicker separation from the patch. They canalso be formulated to release active over extended periods.Alternatively, the microneedles can be designed to rapidly separate fromthe patch, but then dissolve away slowly. A combination of these releasefeatures can be contained within a single microneedle patch to providethe desired release profile of the agent.

In one embodiment, a method is provided for administering a substance ofinterest to a patient, which includes providing one of the microneedlearrays described herein; and applying the microneedles of the array to atissue surface of the patient, wherein the insertion of the microneedlesof the array into the skin is done manually without the use of aseparate or intrinsic applicator device. In this particular context, theterm “applicator device” is a mechanical device that provides its ownforce, e.g., via a spring action or the like, which serves as theprimary force to drive the microneedle array against the tissue surface,separate from any force the user may impart in holding the device and/ormicroneedles against the tissue surface.

5. EXAMPLES

The present invention may be further understood with reference to thefollowing non-limiting examples.

Example 1 Fabrication of a Microneedle Array Mold

A laser-engineered funnel based polydimethylsiloxane (PDMS, Sylgard 184,Dow Corning, Midland, Mich.) microneedle array mold was prepared on thesurface of 2.0-mm-thick PDMS sheet using a Universal Laser systems (VLS3.50). The microneedle array mold included multiple cavities, whereineach cavity included a first cavity and a second cavity. The firstcavity defined a primary funnel portion with 300-700 μm in height and500-1000 μm in diameter at the widest point. The second cavity defined aconical microneedle with 600-900 μm in height, 250-300 μm in diameter atthe widest point, and ˜10 μm in tip radius.

Example 2 Fabrication of a Microneedle Array Molds

A polylactic acid (PLA) microneedle master structure was made by castingmolten PLA pellets (L-PLA, 1.0 dL/g, Birmingham Polymer, Pelham, Ala.)onto the PDMS multi-cavity mold prepared in Example 1 under vacuum at−91 kPa for 1 h at 195° C. After which, PDMS multi-cavity moldreplicates were then made by curing PDMS on top of the PLA masterstructure at 37° C. overnight.

Example 3 Fabrication of a Microneedle Array

A microneedle matrix material was prepared with polyvinyl alcohol (PVA)(MW 2000, ACROS Organics, Geel, Belgium) and sucrose (Sigma-Aldrich, StLouis, Mo.) at a 1:1 mass ratio. Eight grams of PVA was dispersed in 15ml of DI water at 25° C. and then heated to 90° C. for 1 hour tosolubilize to form a PVA solution. After which, 6.0 g of sucrose wasadded and mixed homogeneously with the PVA solution. The resultingmixture was then heated for 2 hours and then centrifuged at 2000×g for30 minutes to remove air bubbles in the mixture to form the microneedlematrix material. The microneedle matrix material was then cooled to 4°C. before use.

A model drug solution was prepared with Sulforhodamine B (MW 559 Da,Molecular Probes Eugene, Oreg.), a water-soluble, red fluorescent dyewith excitation/emission peaks of 565/586 nm, in deionized water. Themodel drug solution was then pipetted onto the top surface of a PDMSmulti-cavity mold to cover all the cavities and then was vacuumed atroom temperature to −91 kPa for 3 minutes. After vacuuming, residualdrug solution on the top surface of the PDMS multi-cavity mold waspipetted off and recycled for reuse. The PDMS multi-cavity mold was thendried under centrifugation at 3000×g at room temperature for 5 minutes.After which, dried Sulforhodamine B adherent to the top surface of thePDMS multi-cavity mold was removed by Scotch tape (3M, St. Paul, Minn.).

Approximately 200 μL of the microneedle matrix material was then appliedto the top surface of the PDMS multi-cavity mold to cover all thecavities. After which, the PDMS multi-cavity mold was vacuumed at roomtemperature to −91 kPa for 3 minutes, and followed by centrifugation at3000×g at room temperature for 5 minutes to remove bubbles.

The PDMS multi-cavity mold, filled with Sulforhodamine B and themicroneedle matrix material, was then freeze-dried in a lyophilizer(VirTis Wizerd 2.0 freeze dryer, Gardiner, N.Y.) for approximately 24hours. The freeze-drying steps were programmed as follows: the mold wasfrozen to −40° C. for 1 hour, and then vacuumed at 2.67 Pa at −40° C.for 10 hours. While the pressure was kept constant (2.67 Pa), thetemperature was gradually ramped up to 0° C. for 1 hour, 20° C. for 1hour, and 25° C. for another 10 hours. After lyophilization, theresulting microneedle array was removed from the PDMS mold using adouble-sided tape (444 Double-Sided Polyester Film Tape, 3M, St. Paul,Minn.). Various microneedle arrays were prepared as disclosed in thisexample. The structural parameters of each microneedle array aresummarized in the table below.

Microneedle Funnel Portion Base Top Base Total Microneedle Heightdiameter Volume Height diameter diameter Base Volume volume Array (μm)(μm) (nL) (μm) (μm) (μm) angle (nL) (nL) 1 700 300 16 300 300 1030 40°115 131 2 700 300 16 300 300 800 50° 76 92 3 700 300 16 300 300 650 60°56 72 4 700 300 16 400 300 965 50° 137 153 5 700 300 16 500 300 1150 50°230 246 6 600 300 14 650 300 1050 60° 257 271 7 750 300 18 650 300 105060° 257 275 8 900 300 21 650 300 1050 60° 257 278

FIG. 17 is a microphotograph of a microneedle array prepared asdisclosed in this example. As illustrated in FIG. 17, the model drug,Sulforhodamine B, is primarily located in the microneedles of theresulting microneedle array (i.e., more of the substance of interest islocated in the microneedles than is located in the funnel portions).

Example 4 Drug Loading Capacity and Efficiency in a Microneedle Array

Six different microneedle arrays prepared as described in Example 2,each containing different drug concentrations (i.e., 0.1 mg/mL, 1.0mg/mL, 5 mg/mL, 10 mg/mL, 15 mg/mL, and 20 mg/mL), were each dissolvedin 10 mL of deionized water in separate containers for 1 hour at roomtemperature. Each dissolved microneedle array was then transferred into96-well plates and measured by in a microplate reader (Multi-modemicroplate Synergy™ MX, Biotek) and analyzed with the Gen5™ software(Biotek). The basis for this experiment was the measurement of theemission/excitation spectrum of Sulforhodamine B, which was linearlyproportional to the Sulforhodamine B concentration over a range of 0.001μg/mL to 1 μg/mL. The average value of the signal for each microneedlearray was used to determine the total amount of drug encapsulated in themicroneedles and funnels (A_(MN+F)) of the microneedle array. The drugloading for each of the six microneedle arrays is shown in FIG. 22. Thedrug loading efficiency for each drug of the six microneedle arrays isdepicted in FIG. 23.

Example 5 Evaluation of Drug Delivery Efficiency of a Microneedle Array

A study was conducted to measure the drug delivery efficiency of amicroneedle array via in vitro testing using porcine cadaver skin(Pel-Freez, Rogers, Ark.). The porcine cadaver skin, initially frozen,was first thawed to room temperature, and then shaved to remove all hairusing a disposable razor (Dynarex, Orangeburg, N.Y.). The subcutaneousfat of the porcine cadaver skin subsequently was removed by a scalpel(Feather, Osaka, Japan).

Microneedle arrays prepared as described in Example 2, each withdifferent sized cavities (primary funnel portions and microneedlescontaining Sulforhodamine B), were each manually inserted into theporcine cadaver skin for 5 seconds, 30 seconds, 1 minute, 2 minutes, 10minutes, and 20 minutes. Each subset of microneedle arrays for eachinsertion time had 6 replicates. After each microneedle insertion, themicroneedle array was microscopically imaged under the microscope(Olympus SZX16, Pittsburgh, Pa.) to determine whether the microneedlesfailed to insert (bent) or inserted, the amount of microneedle dissolvedin the porcine cadaver skin, and whether part of the primary funnelportions dissolved in the porcine cadaver. The insertion site on theporcine cadaver skin was also observed using a microscope to determinewhether the drug was delivered in the porcine cadaver. Adhesive tape(3M, St. Paul, Minn.) was then applied to the insertion site of theporcine cadaver skin to strip off the residual drug left on the skinsurface.

After each insertion time, the tape and post insertion microneedlearrays were placed in separate containers of 10 mL of deionized waterfor 1 hour at room temperature to dissolve. Samples of the dissolvedtape and dissolved microneedle arrays were then transferred into 96-wellplates and measured by in a microplate reader (Multi-mode microplateSynergy™ MX, Biotek) and analyzed with the Gen5™ software (Biotek). Thebasis for this experiment was the measurement of the emission/excitationspectrum of Sulforhodamine B, which was linearly proportional to theSulforhodamine B concentration over a range of 0.001 μg/mL to 1 μg/mL.The average value of the signal for each dissolved tape sample was usedto determine the total amount of drug left on the skin (AF) and theaverage value signal for each dissolved microneedle array was used todetermine the total amount of drug encapsulated in the microneedles andfunnels (A_(MN+F)) of the sampled microneedle array.

FIG. 24 depicts the amount of drug delivered to the skin for eachinsertion time using duplicate microneedle arrays containing 1.0 mg/mLof drug and having the following structural parameters: each cavity ofthe microneedle array, having a total volume of 275 nL, with a firstcavity, defining a primary funnel portion with a height of 650 μm, adiameter of 1050 μm at its widest point, a volume of 257 nL, and a baseangle of 60 degrees, and a second cavity, defining a microneedle with aheight of 750 μm, a base diameter of 300 μm, and a volume of 18 nL. Theamount of drug delivered into the skin (A_(MN)) was determined using thefollowing equation:A _(MN) =A _(F) −A _(MN+F)

-   -   wherein:        -   A_(F)=amount of drug left on the skin and in the funnels        -   A_(MN+F)=total amount of drug contained in the microneedle            array            The drug delivery efficiency of each microneedle array was            defined as:

$\left( \frac{A_{MN}}{A_{{MN} + F}} \right) \times 100$

-   -   wherein:        -   A_(MN)=amount of drug delivered to the skin        -   A_(MN+F)=total amount of drug contained in the microneedle            array

Example 6 Fabrication of a Microneedle Array Using MicrochannelStructure

A microneedle array was formed in which mold filling was accomplishedusing a microchannel structure. FIG. 26 illustrates a cross-sectionalview of a multi-cavity PDMS mold 2602 coupled to a thin film cellmicrochannel structure 2604 and closed on top by a thin polymer lid2606. The microchannel structure 2604 was made with a thin adhesivelayer and includes a microchannel 2608 connecting multiple microneedlecavity arrays spaced across the surface of the mold 2602. Only onemicroneedle cavity array 2610 is shown in FIG. 26. A model drug solution(sulforhodamine) was fed (via a syringe acting as a pump) through thechannel 2608 (as shown in the left side of the figure) and a vacuum wasapplied for 10 minutes (27 in Hg vaccum) to the underside of mold 2602(via a vacuum plate) causing the dye solution to be pulled into thecavities of the mold 2602 (as shown in the right side of the figure).The direction of flow of the dye solution through the channel is to bevisualized and into/out of the page. Then, the dye solution remainingthe channel 2608 was purged with air, forming the microneedles of themicroneedle array.

The dye was allowed to dry, and then a fish gelatin and sucrose solutionwas cast over the mold. Vacuum was applied as before for 30 minutes andthe microneedle arrays were allowed to dry and then were demolded. Thepatches were dissolved in dionized water and assayed for fluorescence.The results confirmed that the dye was loaded into the microneedles.

Example 7 Fabrication of a Microneedle Array

A microneedle multi-cavity mold was formed by 3D printing. Portions ofthe microneedle mold were 3D printed as tapered frustums (steppedsidewalls), each with a height of 1.0 mm and a diameter of 2.0 mm at thewidest point, to form the funnel portion (positive). The 3D printedstructure was then cast with PDMS to create a mold of the funnel bases.A Universal Laser System (VLS 3.50) was then used to form themicroneedle portion (negative) at the center of the funnel portion(negative) of the PDMS to produce a microneedle multi-cavity mold.

A model drug solution was then deposited onto the top surface of theresulting microneedle multi-cavity mold and then dried. A melted bulkingpolymer was then cast over the resulting microneedle multi-cavity moldand then cooled/solidified. The resulting microneedle array was thenremoved from the microneedle cavity mold.

Example 8 Vacuum-Assisted Filling Through Mold

A vacuum plate for receiving a multi-cavity mold was designed, built,and evaluated. The vacuum plate and mold are shown in FIG. 18.

A mold made from polydimethylsiloxane (PDMS) (DC Sylgard 184) was usedwith the vacuum plate. The mold was 2 mm thick. Solutions of variousviscosities were prepared and applied as a thin layer on the top surfaceof the mold. The solutions were water with 0.4% dye, a 40 wt %polyvinylpyrrolidone (PVP) solution, a 60 wt % PVP solution, and asolution of soldium carboxymethyl cellulose (CMC) and trehalose (1:1)(25% solids). A vacuum pressure of −13.8 psi was applied to the lowerside of the mold for various periods of time. Whether microneedle cavityfilling was achieved was then assessed.

The results are shown in the table below, and generally show thatmicroneedle molds can be filled within 3 minutes by applying vacuumthrough the underside of the mold and that the time to remove the airand fill the mold with solution was not strongly influenced by thesolution viscosity over the range considered.

Approximate Viscosity Time Successful Solution (cP) (minutes) Fill?Water/dye 1 1 No Water/dye 1 2 No Water/dye 1 3 Yes 40% PVP 100 3 Yes60% PVP 1000 3 Yes CMC: Trehalose ∞ 3 Yes

Example 9 Pressure-Assisted Filling Through Mold

A pressure assisted fill of a microneedle mold was evaluated. The moldwas made from PDMS (DC Sylgard 184) and was 2 mm thick. Solutions ofvarious viscosities were prepared and applied as a thin layer on the topsurface of the mold. The solutions were water with 0.4% dye, a 40 wt %polyvinylpyrrolidone (PVP) solution, and a 60 wt % PVP solution. Apressure of 50 psi or 65 psi was applied to the upper side of the mold(for a pressure differential across the mold of 35 or 50 psi, givenatmospheric pressure of ˜15 psi) for various periods of time. Whethermicroneedle cavity filling was achieved was then assessed.

The results are shown in the table below, and generally show that byapplying modest amounts of pressure to the solution, one is able toforce the solution down into the cavities and to force the air outthrough the mold or into the solution itself within 20 seconds. Theresults also show that the time to remove the air and fill the mold withsolution was not strongly influenced by the solution viscosity under theconditions studied.

Approximate Viscosity ΔP Time Successful Solution (cP) (psi) (seconds)Fill? Water/dye 1 35 20 No Water/dye 1 35 30 Yes 40% PVP 100 35 30 Yes60% PVP 1000 35 30 Yes 40% PVP 100 50 20 Yes 60% PVP 1000 50 20 Yes

While the invention has been described in detail with respect tospecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereof.

We claim:
 1. A microneedle array for administration of a substance ofinterest into a biological tissue, the array comprising: a basesubstrate having a microneedle side and an opposing back side; a primaryfunnel portion extending from the microneedle side of the basesubstrate, the primary funnel portion consisting of a single funnel; andtwo or more solid microneedles extending from the single funnel, whereinthe two or more solid microneedles comprise a substance of interest. 2.The microneedle array of claim 1, wherein each of the two or more solidmicroneedles further comprises a secondary funnel portion extending fromthe primary funnel.
 3. The microneedle array of claim 1, wherein theprimary funnel portion comprises a straight, tapered sidewall.
 4. Themicroneedle array of claim 1, wherein the primary funnel portioncomprises a hemispherical sidewall.
 5. The microneedle array of claim 1,wherein the primary funnel portion comprises a stepped sidewall.
 6. Themicroneedle array of claim 1, wherein the substance of interestcomprises an active pharmaceutical ingredient.
 7. The microneedle arrayof claim 1, wherein the two or more solid microneedles are formed of acomposition comprising a water soluble matrix material in which thesubstance of interest is dispersed.
 8. The microneedle array of claim 7,wherein the primary funnel portion is formed of a composition comprisingthe water soluble matrix material.
 9. The microneedle array of claim 7,wherein the water soluble matrix material comprises polyvinyl alcohol,dextran, carboxymethylcellulose or maltodextrin, and a sugar.
 10. Themicroneedle array of claim 1, wherein the ratio of the height of theprimary funnel portion to the height of the each of the two or moremicroneedles is from 0.3 to
 4. 11. The microneedle array of claim 1,wherein the two or more microneedles have a length from 200 μm to 1200μm.
 12. The microneedle array of claim 2, wherein the secondary funnelportion comprises a straight, tapered sidewall.
 13. The microneedlearray of claim 2, wherein the secondary funnel portion comprises ahemispherical sidewall.
 14. The microneedle array of claim 2, whereinthe secondary funnel portion comprises a stepped sidewall.
 15. Themicroneedle array of claim 2, wherein the secondary funnel portion isintegrally formed with the primary funnel portion.
 16. The microneedlearray of claim 15, wherein the secondary funnel portion is formed of acomposition comprising a water soluble matrix material.
 17. Amicroneedle patch comprising: the microneedle array of claim 1; anadhesive layer; and a handle layer affixed to the base substrate,wherein the handle layer comprises a tab portion which extends away fromthe one or more solid microneedles and permits a person to manually holdthe tab portion to manipulate the patch without contacting the two ormore solid microneedles.
 18. A microneedle array for administration oftwo or more substances of interest into a biological tissue, the arraycomprising: a base substrate having a microneedle side and an opposingback side; a first funnel portion extending from the microneedle side ofthe base substrate, wherein the first funnel portion is elongated in adirection parallel to the base substrate; and a first array of two ormore solid microneedles extending from the first funnel portion, whereinthe microneedles of the first array comprise a first substance ofinterest; a second funnel portion extending from the microneedle side ofthe base substrate, wherein the second funnel portion is elongated in adirection parallel to the base substrate; and a second array of two ormore solid microneedles extending from the second funnel portion,wherein the microneedles of the second array comprise a second substanceof interest, which is different from the first substance of interest.19. The microneedle array of claim 1, comprising two or more primaryfunnel portions.
 20. The microneedle array of claim 19, wherein each ofthe primary funnel portions is laterally spaced from at least one otherneighboring primary funnel portion.